Iowa Monthly Climate Summary – June 2016

Temperatures

The statewide monthly average temperature was 73.2°F or 3.5°F above normal (See Figure 1). June 2016 ranks as the 14th warmest June among 144 years of statewide climate records. A warmer June was last recorded in 1991. The average temperature at Des Moines and Waterloo was 77.3°F and 71.9°F respectively.  Des Moines was 5.5°F above normal while Waterloo was only 1.9°F above its monthly average. On the 15th, the hottest temperature of 96°F was recorded for the month at Des Moines while the coldest temperature was 56°F on the 2nd. The hottest temperature at Waterloo was 95°F on the 10th while just two days earlier the low temperature dropped to 46°F.

Above normal temperatures prevailed for the majority of month of June across the state. A long hot spell occurred from the 9th to the 20th when the hottest temperature of 100°F was recorded at Little Sioux on the 11th (See Figure 2). This 100°F ended up being the hottest temperature for the entire state during June 2016 and was Iowa’s first triple-digit temperature since September 10, 2013. The state’s second longest streak without a 100°F reading ended on the 11th with 1,004 consecutive days. The longest streak is 1,438 consecutive days from August 3, 1991 to July 9, 1995.  The maximum temperature at Des Moines from the 9th to the 27th was 85°F or higher for 19 consecutive days in June.  This became the longest streak of its kind during the month of June since 1878 at Des Moines. The previous longest stretch was 17 consecutive days set in June 1956.

Precipitation

The statewide average precipitation was 3.69 inches which was 1.33 inches below the state’s normal for June (See Figures 3 & 4). This ranks as the 45th driest June out of 144 years of statewide climate records. The monthly totals at Des Moines and Waterloo were 1.47” or 3.47” below normal and 8.97” or 4.98” above normal. Des Moines recorded its 10th driest June since 1878 and Waterloo recorded its 4th wettest June since 1895. This was common throughout the state as the precipitation was highly variable (See Figure 5). For example, Cedar Falls had a whopping 11.22” while Salem only recorded 0.25” for the entire month. By the end of the month, much of south central to southeast Iowa were placed into Moderate Drought by the U.S. Drought Monitor with much of the southwest to western part of the state classified as Abnormally Dry (See Figure 6). Severe weather was limited throughout the month of June, even though June is Iowa’s peak severe weather month. In fact, the first half of 2016 was fairly “quiet” with respect to severe weather (See Figures 7a/7b).  The most active day came on June 14th when several central to northern Iowa counties reported wind damage. Heavy rain and damaging winds plagued a few counties during the evening of the 25th into the early morning on 26th (See Figure 8). Flooding was also limited during the month with only 1 river reaching flood stage and just a handful of Flash Flood Warnings issued by National Weather Service Office in Des Moines.

Blog post by Kenny Podrazik, Meteorologist, NWS Des Moines

Iowa Summer Weather Review

Temperatures:

Temperatures have remained warmer than normal for much of the spring into the first half of the summer.  The warm temperatures have been interrupted from time to time by cooler periods, especially in May when monthly temperatures averaged just below normal, but for the most part readings have remained warmer than normal.  The warmest readings have been across western Iowa with a couple periods of intense heat during June and July with heat index values going above 110 degrees during the third week of July.

 

Spring and early Summer temperature departure in Iowa – warmer than normal.

Spring and early Summer temperature departure in Iowa – warmer than normal.

Precipitation:

Since the beginning of March, precipitation has been most robust and reliable along the Minnesota border into east central Iowa as well as the far southwest corner of the state.  Much of the remainder of Iowa has seen at or below normal rainfall, especially in central into south central and southeast Iowa.  The month of June was particularly dry in these locations with some areas remaining below one inch of precipitation or only about a quarter of normal.  Recent storms across much of Iowa in July have helped to alleviate the incipient drought conditions in the state, although much of the rain was quickly used by maturing crops.  The map shows the percentage of normal precipitation from the March through July time frame.

Summer rainfall departures – Wet on the edges, dry central and southeast.

Summer rainfall departures – Wet on the edges, dry central and southeast.

Spring 2016 Climate Table
Blog post by Craig Cogil, Senior Forecaster, NWS Des Moines

On This Date in Iowa Weather History – May 6

Iowa certainly has had its extreme weather. May is no exception and today (May 6) has proven that Iowa can experience many different types of weather no matter the season. From snow to tornadoes to extreme heat or bitter cold and not to forget flooding. Below are 6 years of the most extreme weather across Iowa that has occurred on May 6.

  • 1885: A late spring cold spell produced frost and flurries across Iowa from May 6-9, 1885.  On the morning of the 6th it was reported that ice half an inch thick formed on standing water in Muscatine County. Flurries were reported at Sibley, St. Ansgar, and Waukon that morning and at other stations across northern Iowa on the following two days. The cold spell resulted in widespread damage to garden plants, orchards, and other vegetation across the state.
  • 1890: Unseasonably cold weather resulted in light snow mixed with rain and sleet in some areas. At Des Moines the Weather Bureau observer reported a trace of snow, while at Amana the observer wrote that ‘snow fell on the 6th, covering ground to a depth of one inch, but all melted by noon.’
  • 1934: One of the hottest summers on record in Iowa began in earnest as the temperature reached 100 F at Sioux City where this remains the earliest date of triple digit heat on record. This was only the first of a remarkable 11 days that month on which a 100 F or higher temperature was recorded somewhere in Iowa. Other reported high temperatures included 100 F at Alton, 99 F at Le Mars, Storm Lake, and Waterloo, 98 F at Algona and Grinnell, and 97 F at Atlantic, Fayette, and Washington. At Des Moines the month would finish as the warmest May on record with an average temperature of 71.1 F. A couple figures in the slideshow below shows the maximum temperatures and their departure from normal.
  • 1971: Severe weather struck southwestern Iowa for the second consecutive day. After an F3 tornado on the 5th injured 12 people in Taylor County as it passed through the town of Conway, a severe hail storm on the 6th dropped stones 2 inches in diameter in Mills County for such duration that they drifted 2 to 3 feet deep in the ditches and gullies around Glenwood.
  • 1983: A tornado touched down briefly in Pleasant Hill on the eastern edge of Des Moines, producing F2 damage as it destroyed 11 homes and damaged about two dozen more on a path only 8 to 10 blocks long and 50 to 75 yards wide. Several other tornadoes touched down across central and southwestern Iowa that evening but produced only minor damage with no injuries.
  • 1989: Unseasonably cold air settled across Iowa for the first week or two of May. The coldest temperatures were reached on the 6th when flurries were reported at most locations in the state and Hampton measured a tenth of an inch of snow. Temperatures bottomed out in the 20s at most stations north of I-80 and in the low to mid 30s to the south with the lowest readings including 26 F at Allison, Fayette, and Oelwein, 25 F at nine stations including Decorah, Forest City, and Hampton, 24 F at Charles City and Colo, and 23 F at Cresco. The low temperatures across Iowa were 12 to 18 degrees below normal! See the slideshow below for a map of where the coldest temperatures were located on May 6, 1989.

This slideshow requires JavaScript.

For more On this Date in Iowa Weather history, please visit our website at: http://www.weather.gov/dmx/wxHistory

 

Iowa Monthly Climate Summary – April 2016

This slideshow requires JavaScript.

Temperatures

The statewide average temperature was 49.9°F or 1.0°F above normal (See Figure 1). April 2016 became the 57th warmest April out of 144 years of statewide climate records.  The monthly average temperature at Des Moines was 54.2°F or 2.5°F above normal which was the 22nd warmest March for that station since records began in 1878. At Des Moines, the highest temperature was 83°F on the 3rd and the lowest was 25°F on the 9th.  Waterloo’s monthly average temperature was 49.1°F or 0.2°F above normal. The highest temperature at Waterloo was 80°F on the 16th while the coldest was 16°F on the 9th.

At the beginning and end of the month, temperatures were generally below normal. During the middle weeks of April is when the above normal temperatures prevailed. The warmest period occurred from the 13th to the 26th (See Figure 2). A pair of hard freezes occurred on the 9th and 12th of the month where the 9th was the coldest day across the state (See Figure 3). The coldest temperature of the month was 13°F in Audubon on the 9th. Sheldon, Spencer, and Webster City all recorded 16°F low temperatures on the morning of the 12th.  The month’s highest temperature was 85°F at Little Sioux on the 3rd and then Donnellson reached the same temperature on the 25th. Dreary and damp weather set in across the state during the final four days of the month and kept temperatures well below normal, especially maximum temperatures (See Figure 4).

Precipitation

The statewide precipitation total was 3.07 inches or 0.44 inches below normal. For the entire month, precipitation totals were above normal across western Iowa while the north central to northeast had the lowest amount of precipitation (See Figure 5). April 2016 became the 68th wettest April among 144 years of climate records.  The total precipitation at Des Moines was 3.37 inches or 0.49 inches below normal while Waterloo totaled 2.60 inches or 1.11 inches below normal for the month.

Abnormally dry weather conditions reigned during the first 18 days of April when no measurable precipitation occurred over west central to southwest Iowa (See Figure 6). During the last 12 days of the month, a more active and wet pattern developed across the state (See Figure 7). In fact, the statewide average precipitation during the first 18 days was 0.57 inches, while the final 12 days averaged 2.50 inches.  The hardest hit area was western Iowa the last 2/5 of the month and caused several rivers and streams to become bank full or even reached minor flood stage by early May. April 2016 totals ranged from 0.75 inches at Marquette to 7.52 inches at Alta.  Another comparison, Guttenberg had its driest April since 1942 while Sioux City recorded its wettest April since 1998.  A cold, dreary, and soggy end to the month plagued the entire state, but the precipitation totals were recorded on the morning of the 1st of May and will be recorded in the May 2016 precipitation total.

There was very little severe weather throughout the month as the first 18 days were fairly inactive. Only 2 days had severe weather which were the 24th and 27th of April. Northwest Iowa had high winds and large hail on the 24th while on the 27th had 5 tornadoes that occurred in southwest Iowa, including an EF1 in Stanton, Iowa. For a summary of the event, visit: http://www.weather.gov/dmx/160427summary. As far as non-thunderstorm activity, there were several high wind events that occurred during the first 8 of 9 days of the month.  This is not uncommon as early April is typically the windiest time of year in Iowa.

Blog post by Kenny Podrazik – NWS Des Moines

15-Year Anniversary of Agency, Iowa Tornado

On April 10-11, 2001, a significant severe weather outbreak produced 28 tornadoes across Iowa which was part of a region wide 2-day tornado outbreak that spawned 79 tornadoes across Nebraska, Iowa, Kansas, Missouri, Oklahoma, and Texas.  The 28 tornadoes in Iowa became an all-time state record for tornadoes in a single day.  The majority of these tornadoes were toward the weaker end of the Fujita scale.  However, an F2 struck Agency, Iowa in Wapello County that caused two deaths and three injuries.  Another tornado, a long-lived tornado, tracked from northern Missouri to Madison County and caused extensive damage in Ringgold County.  In addition to the widespread tornadoes, large hail was also reported ranging up to golf ball size at Parkersburg and there were scattered reports of 70 to 85 mph wind gusts with the worst straight-line wind damage in Black Hawk and Franklin counties.

A very strong low pressure system moved from central Kansas into southeast Nebraska on April 11, 2001.  A warm front extended east along the Missouri/Iowa border during the late morning and surged northward throughout the afternoon (see the 3 hand drawn surface analysis below).  A dryline oriented northwest-southeast moved from southwest Iowa into central to south-central Iowa in the afternoon. Storms erupted along this dryline in the afternoon, but there were also storms that focused along the warm front.  As you can see from Figure 1 below, the radar operator had a very busy day identifying the rotation within each storm that were rapidly moved north-northeast through the afternoon hours. There were 12 tornadoes that occurred within the NWS Des Moines county warning area. 

RotationalTracks

Figure 1: Operator identified low-level mesocyclone tracks on 11 April 2001 between 1900-2130 UTC (2:00 PM CDT to 4:30 PM CDT). The dots indicate location of the rotation center every 5 minutes and the dash indicates that a “cell” was still identifiable on radar, but no velocity couplet was found. “FO” or “F1″ to the right of the tracks indicate location of tornadoes and Fujita scale intensity. The “M” to the left of track indicates WSR-88D mesocyclone detection and the “MA” has a base above 5 km. From Figure 1 via Karl A. Jungbluth; “The Tornado Warning Process During a Fast-Moving Low-Topped Event: 11 April 2011 in Iowa.”

 

18Z_sfc
1800 UTC (1:00 PM CDT) 11 April 2011

20Z_sfc
2000 UTC (3:00 PM CDT) 11 April 2011

21Z_sfc
2100 UTC (4:00 PM CDT) 11 April 2011

 

F1 damage to a barn three miles northwest of Murray, Iowa along the Union and Clarke county line. Three cows were killed along with multiple large trees down. NWS Des Moines Survey.

F3 damage to an apparently well built home. The destruction included the roof being completely gone and several interior and exterior walls destroyed. Location of the home was along highway 2 one mile east of Mount Ayr, Iowa. NWS Des Moines survey.

F2 damage along J55 three miles north of the Missouri border, or seven miles south of Mounty Ayr, Iowa. A partial underground home severely damaged. Roof completely off and destroyed. Interior walls and main wall facing south remained intact limiting damage to F2. NWS Des Moines survey.

F2 damage along P38 1.5 miles north of the Missouri border. Weak structure, or old house, that was completely destroyed. This was similar to a mobile home being destroyed. NWS Des Moines survey.

agengy dmg photoA damaged home in Agency, Iowa.

Blog post by Kenny Podrazik – NWS Des Moines

Reference: Karl A. Jungbluth; “The Tornado Warning Process During a Fast-Moving Low-Topped Event: 11 April 2011 in Iowa.

 

April 8-10, 1973 – Iowa Blizzard

StateSnowfallTotals-April8-10-1973

Snowfall totals from April 8-10, 1973 across Iowa. The highest total was 20.3 inches in Belle Plaine, Iowa (Benton County). Des Moines Totaled 14.0 inches from this storm.

In 1973, possibly the worst April blizzard on record in Iowa pounded the state from April 8-10. Snowfall totals of 20.3 inches at Belle Plaine and 19.2 inches at Dubuque set all-time storm total records at those locations. Total amounts of 16.0 inches were reported at Lansing and New Hampton, while Cedar Rapids received 14.5 inches, Iowa City 14.3 inches, and Des Moines 14.0 inches. At Des Moines 10.3 inches of their total fell just on the 9th, making it the snowiest April day on record at that location. Winds gusting to 65 mph or higher resulted in near zero visibility and blew the snow into drifts as deep as 16 feet closing most roads in the state.

MondayApril091973SurfaceMap

Surface map on the morning of April 9, 1973 shows the strong low pressure center over southeast Iowa and northern Illinois. Much of Iowa was receiving strong winds and blowing snow at this time.

TuesdayApril101973SurfaceMap

Tuesday morning April 10, 1973, the blizzard was winding down across the state.

73blizzard

Bell Avenue and Fleur Drive on April 9, 1973. Image courtesy of Des Moines Register.

blizzard4

April 1973 Blizzard aftermath. Unknown location.

 

 

Here are a few other blog posts about this storm:
http://ourpreciousmemories.ning.com/profiles/blogs/april-1973-blizzard-in-iowa
http://www.iowalivingmagazines.com/2013/03/27/april-blizzard-of-73/
http://dmpl.org/blog/local-history/blizzard-1973#.Vwojr3p7ZCB
http://www.iawx.net/2013/04/05/historical-wx-april-blizzard-of-1973/#prettyPhoto

Blog post by Kenny Podrazik – NWS Des Moines

 

September 2015 Iowa Climate Review

Temperatures

The average statewide temperature during the month of September was 68.5°F which was 5.3°F above normal (See Figure 1). September 2015 became the 7th warmest September among the 143 years of state climate records. Des Moines’ average monthly temperature was 71.9°F or 6.3°F above normal. The coldest temperature of the month at Des Moines was 47°F on the 30th while the hottest temperature reached 94°F on the 6th. Waterloo was also well above normal for monthly average temperature with an average of 68.3°F or 5.3°F above normal. The coldest temperature at Waterloo in September was 39°F on the 30th while the warmest temperature was 92°F on the 6th. 90 degree temperatures were fairly common during the first week of September. In fact, the first seven days of the month were the warmest week of the year in the state with temperatures averaging 10.6° above normal (See Figure 2).

When temperatures were above normal during September, they were well above normal with some of the warmest stretches occurring from the 3rd to 7th, 15th to 17th, and 22nd to 25th. In fact, Des Moines had more days (13) when the average daily temperature was at least 10°F greater than normal, than it had days when the average temperature dropped below normal (7). Waterloo only had 6 days when the daily average temperatures was below normal and had 11 days when daily average temperature was at least 10°F or greater than normal. A cold front pushed through the state at the end of the month and brought some temperatures in the 30s across northern Iowa. Estherville and Cresco dropped to 33°F on the 30th.

Figure 1: Average temperature departure from normal for the month of September 2015. Map is courtesy of MRCC.

Figure 1: Average temperature departure from normal for the month of September 2015. Map is courtesy of MRCC.

Figure 2: Average temperature departure from normal during the first week of September 2015. Map is courtesy of MRCC.

Figure 2: Average temperature departure from normal during the first week of September 2015. Map is courtesy of MRCC.

















Precipitation

The average statewide precipitation was 4.08 inches or only 0.70 inches above normal (See Figure 3). September 2015 becomes the 50th wettest September among 143 years of statewide records. It was a “hit-or-miss” for precipitation during the month of September with the west to southwest portions of the state receiving the bulk of the rain and the north to east the less amounts (See Figure 4). Typically when it rained in September, it rained in abundance but in isolated areas. Fort Dodge for instance only received 0.90 inches while Glenwood reported 11.63 inches for the month. Des Moines and Waterloo had 5.25 inches and 2.59 inches respectively. Torrential rains fell over portions of central to southwest Iowa during the overnight hours from the 6th to the 7th and caused some significant flash flooding in Carroll, Guthrie, and Greene counties. The towns of Bagley, Coon Rapids, Bayard, Glidden, and Carroll all had significant impacts due to flash flooding (See Figure 5), with major state Highway 141 receiving water over it in multiple locations. Radar estimated rainfall amounts ranged from 3 to 8 inches on the night of the 6th (See Figure 6) with a report of 6.25 inches from a spotter in Bagley. Portions of southeast Iowa also had 2 to 4 inches of rain from the 6th to 7th. On the 23rd, western Iowa received a round of torrential rain and mainly affected the Council Bluffs area. In fact, a storm total of 9.28 inches was reported on the north edge of Council Bluffs. Severe weather was fairly limited across the state during the month of September with a few reports of large hail and damaging winds on the 6th and then again on the 10th to the 11th.

Figure 3: September 2015 total precipitation for the month across Iowa shows the west to southwest received the most significant amounts with the far eastern corners of the state the lowest amounts.

Figure 3: September 2015 total precipitation for the month across Iowa shows the west to southwest received the most significant amounts with the far eastern corners of the state the lowest amounts.

Figure 4: Average precipitation departure from normal for the month of September 2015. Map is courtesy of MRCC.

Figure 4: Average precipitation departure from normal for the month of September 2015. Map is courtesy of MRCC.

Figure 5a: Flash flooding photos from Carroll on September 6, 2015. Photos are courtesy of KCCI and Iowa Storm Chasing Network.

Figure 5a: Flash flooding photos from Carroll on September 6, 2015. Photos are courtesy of KCCI and Iowa Storm Chasing Network.

Figure 5b: Flash flooding photos from Carroll on September 6, 2015. Photos are courtesy of KCCI and Iowa Storm Chasing Network.

Figure 5b: Flash flooding photos from Carroll on September 6, 2015. Photos are courtesy of KCCI and Iowa Storm Chasing Network.

Figure 6: Radar estimated rainfall amounts from September 6-7, 2015 show a very heavy swath of rain from Coon Rapids to Bayard to Rippey Iowa.

Figure 6: Radar estimated rainfall amounts from September 6-7, 2015 show a very heavy swath of rain from Coon Rapids to Bayard to Rippey Iowa.

Blog post by Kenny Podrazik – NWS Des Moines

June 24-25 Raccoon River Flooding Review

Blog post by Kenny Podrazik – NWS Des Moines
SVRDMX-0082

Figure 1

SVRDMX-0098

Figure 2

Two periods of storms affected central Iowa during a 24-hour period from June 24 to June 25, 2015.  The first round of storms occurred during the morning hours on June 24 that affected portions of Iowa along and south of Highway 20. This was the “primer” for significant flash flooding and river flooding that would result from the second round of storms to affect the same area later that evening.  The second round of thunderstorms began to develop over west-central Iowa late in the afternoon and quickly became severe by the early evening. The first Severe Thunderstorm Warning (Figure 1) issued by the National Weather Service in Des Moines was at 6:20 p.m. CDT on June 24 for Guthrie and Dallas Counties.  The final Severe Thunderstorm Warning (Figure 2) expired at 1:50 a.m. CDT on June 25 for Marion and Jasper Counties.  There were multiple reports of large hail that ranged from the size of a quarter (one inch) to hen egg (two inches) throughout the night. Winds to 60 mph caused numerous trees to become damaged and there was even a report of an 80 mph wind gust in Guthrie County early in the evening.  Extremely heavy rain brought widespread flash flooding from west-central Iowa to southeast Iowa, including the Des Moines Metro, late in the evening into the overnight hours Thursday morning. The video below shows the entire second round of storms unfold on radar from the first development of a thunderstorm around 6 p.m. CDT on June 24 to the final drop ending around 2 a.m. CDT on June 25.

Widespread rainfall amounts of three to seven inches were reported after the event, with the highest report of 7.25” near Dawson, Iowa in northwest Dallas County.  From Bagley to Jamaica, Iowa, radar estimated near nine inches of rain fell within this area of the upper reaches of the Raccoon River Basin. The majority of the heaviest rain fell within the Raccoon River Basin (Figure 3).  As a result, major to near record flooding occurred along the Raccoon and Des Moines River Basins, including several tributaries (Figure 4).  In fact, the Walnut Creek recorded its highest crest ever at two river gauge locations. The Clive I-80/35 (CLVI4) and Des Moines 63rd Street (DOSI4) gauges crested at 13.41 feet and 18.82 feet respectively, both breaking the previous records set back on August 9, 2010.  Near record flooding occurred on portions of the Raccoon River, with Van Meter (VNMI4), Des Moines Highway 28 (DMWI4) (Figure 5), and Des Moine Fleur Drive (DEMI4) all cresting at their third highest crest in history. All the flooding on the Des Moines and Raccoon subsided by June 29, 2015.

Storm Total Radar Estimated Precipitation ending 7 am June 25, 2015. The yellow oval received 6-9 inches of rainfall in the headwaters of the Raccoon River Basin.

Figure 3: Storm total radar estimated precipitation ending 7 am June 25, 2015. The yellow oval received 6-9 inches of rainfall in the headwaters of the Raccoon River Basin.

June 2015 crests along central Iowa Rivers.

Figure 4: June 2015 crests along central Iowa Rivers.

Figure 3: Hydrograph of the Raccoon River at Des Moines Highway 28 shows it crested just above major flood stage (purple) on June 26, 2015.

Figure 5: Hydrograph of the Raccoon River at Des Moines Highway 28 shows it crested just above major flood stage (purple horizontal line) on June 26, 2015.

August 2015 Iowa Monthly Climate Review

Temperatures

The statewide average temperature for Iowa in August 2015 was 69.2°F which was 2.3°F below normal (See Figure 1). August 2015 became the 27th coolest August out of 143 years of records for the state of Iowa. This is the 4th consecutive month with the temperatures being below normal. Actually, throughout the month of August 2015, there were no long duration heat waves, just a few isolated days reaching the lower 90s early in the month. The hottest temperature in the state during the entire month was only 94°F at Sheldon on the 2nd. Des Moines recorded 93°F on the same day and that was 1 of only 2 days in which Des Moines reached 90°F or greater. The 2nd time was on the 7th when it reached 90°F on the nose. The coldest temperature throughout the month was 40°F in Spencer on the 25th. The coldest high temperature at Des Moines was 68°F on the 19th and the lowest temperature was 53°F on the 25th and 26th. Waterloo reached exactly 90°F only once and that occurred on the 2nd and its coldest temperature in August was 45°F on the 26th. On the 18th and 19th, Waterloo had back-to-back days of highs remaining in the 60s and from the 18th to the end of the month, only 2 days had a daily average temperatures that were above normal. Waterloo for the month was 2.4°F below normal for a monthly average temperature while Des Moines was 1.2°F below normal for a monthly average temperature. In Ottumwa, it was 2.7°F below its normal monthly average temperature for August.

Figure 1: Average statewide monthly temperature departure from normal for August 2015. Image is courtesy of High Plains Regional Climate Center (HPRCC).

Figure 1: Average statewide monthly temperature departure from normal for August 2015. Image is courtesy of High Plains Regional Climate Center (HPRCC).

Precipitation

The average statewide precipitation was 5.42 inches or 1.22 inches above normal for the month of August 2015 (See Figures 2 to 4). This is the 21st wettest August among 143 years of records and was the fourth consecutive month with above normal rainfall. The average statewide precipitation during the first half of August was 1.30 inches which was 0.92 inches below normal. A few light rain events occurred during the first couple of weeks with only one significant severe weather event on the 2nd and a heavy rain event that transpired on the evening of the 8th into the early morning on the 9th. On August 2nd, a tornado brought EF1 damage to Adair and Adams Counties as it was on the ground for 36 minutes covering 7.54 miles (See Figures 5 & 6). During the 8th and 9th, a swath of heavy rain fell from Webster County through Story, Boone, and Jasper Counties and southeast into Poweshiek County where roughly 2 to 5 inches of rain fell (See Figure 7). Heavy rain also fell over portions of far southwest Iowa on the 8th. The highest preliminary rainfall report was 7.00” in Otho, Iowa in Webster County on August 8, 2015. More widespread rain events occurred during the final two weeks of the month when the state averaged 4.12 inches or 2.14 inches above normal during that time frame. Heavy rain fell on the 17th and 18th over central to northwest Iowa (See Figure 8). Des Moines picked up 2.46 inches on the 18th, well over half of its monthly total of 4.25 inches. However, the most notable heavy rain event occurred on the 28th when a widespread 3 to 7 inches fell over portions of central Iowa with an isolated amount over 9 inches reported in Dayton, Iowa in Southeast Webster County (See Figure 9). A major flash flood on the Skillet Creek affected much of the town of Dayton as a result of the large amount of rain (See Figures 10 & 11). One other notable event that was related to weather was a lightning strike on August 23 that struck a corn stover bale storage unit near Maxwell and set it on fire (See Figure 12). The fire blazed for roughly a full day before burning out and was seen on radar for a good portion of the day on August 23 (See Figure 13).

Figure 2: Total precipitation for the state of Iowa during August 2015.

Figure 2: Total precipitation for the state of Iowa during August 2015.

Figure 3: Total precipitation departure from normal for the state of Iowa during August 2015.

Figure 3: Total precipitation departure from normal for the state of Iowa during August 2015.

Figure 4: Total precipitation percent of mean for the state of Iowa during August 2015.

Figure 4: Total precipitation percent of mean for the state of Iowa during August 2015.

Figure 5: August 2, 2015 EF1 tornado track in Adair and Adams County.

Figure 5: August 2, 2015 EF1 tornado track in Adair and Adams County.

Figure 6: August 2, 2015 EF1 tornado track in Adair and Adams County. Photo is courtesy of Adam Amdor via Twitter (@Amdor_7).

Figure 6: August 2, 2015 EF1 tornado track in Adair and Adams County. Photo is courtesy of Adam Amdor via Twitter (@Amdor_7).

Figure 7: August 8-9, 2015 observed precipitation.

Figure 7: August 8-9, 2015 observed precipitation.

Figures 10 & 11: Major Flash Flooding on the Skillet Creek affected the Golf course and Campground in Dayton, Iowa. Photos are courtesy of James Hobbs and Jennifer Eckert.

Figure 10: Major Flash Flooding on the Skillet Creek affected the Golf course in Dayton, Iowa. Photo is courtesy of James Hobbs and Jennifer Eckert.

Figures 10 & 11: Major Flash Flooding on the Skillet Creek affected the Golf course and Campground in Dayton, Iowa. Photos are courtesy of James Hobbs and Jennifer Eckert.

Figure 11: Major Flash Flooding on the Skillet Creek affected the Campground in Dayton, Iowa. Photo is courtesy of James Hobbs and Jennifer Eckert.

Figure 8: Q3 radar estimated precipitation from August 18, 2015.

Figure 8: Q3 radar estimated precipitation from August 18, 2015.

Figure 9: The observed significant amount of rain on August 28, 2015.

Figure 9: The observed significant amount of rain on August 28, 2015.

Figure 12: Lightning started a fire of a corn stover storage unit near Maxwell, Iowa on August 28, 2015. Photo is courtesy of Melissa Spencer, Story County EMA.

Figure 12: Lightning started a fire of a corn stover storage unit near Maxwell, Iowa on August 28, 2015. Photo is courtesy of Melissa Spencer, Story County EMA.

Statewide climate statistics courtesy of State Climatologist Harry Hillaker: http://www.iowaagriculture.gov/climatology/weatherSummaries/2015/pms201508.pdf
Blog Post by Kenny Podrazik – NWS Des Moines