On This Date in Iowa Weather History: Record August Cold

On August 20, 1950, unseasonably cool weather sent the temperature plummeting down to 30°F at Britt and Sibley, Iowa.  This tied the all-time coldest August temperature for Iowa, which previously occurred a full ten days later on the 30th (Elkader in 1893 and Mason City in 1915). At Des Moines the temperature reached 40°F on the 20th, tying the August record at that location. Other low temperatures around Iowa that morning included 31°F at Decorah, 32°F at Clarion and Saratoga, and 33°F at Atlantic, Inwood, Sheldon, and Waterloo. The majority of Iowa was 20 to 25 degrees below normal with respect to low temperatures.

Departure from Normal Minimum Temperatures on August 20, 1950.

Departure from Normal Minimum Temperatures on August 20, 1950.

Low temperatures on the morning of August 20, 1950. Image courtesy of Iowa Environmental Mesonet.

Low temperatures on the morning of August 20, 1950. Image courtesy of Iowa Environmental Mesonet.

Iowa Monthly Climate Summary – May 2015

Temperatures

The statewide (Iowa) average temperature for May 2015 was 60° which was only 0.1° below normal (See Figure 1). May 2015 ranks as the 69th warmest May out of 143 years of statewide records. The month of May witnessed several big temperature swings with the first third of the month (2nd to 10th) beginning well above normal before an extended period of chilly weather (11th to 22nd) settle into Iowa during the middle of the month. The coldest days were from the 18th to 21st where most stations ranged from 10 to 15 below their respective normal values (See Figure 2). Waterloo on the 20th had an average temperature of 45° which was 17 degrees under its normal. There were a couple additional days at the end of the month when the daily average temperature dipped to near 10 below normal. However, prior to the aforementioned two days, temperatures generally ranged slightly above normal. The coldest temperature at Des Moines and Waterloo was 39° (19th) and 34° (1st) respectively. The coldest temperature in the state throughout May was 31° at Elkader and Lowden on the 1st while the hottest temperature was 89° at Little Sioux on the 3rd. In fact, the last time when temperatures did not reach 90° during the month of May was in 1995.

AvgTemp_DfM_May_2015 Figure 1: Average temperature departure from mean during the month of May 2015.

AvgTemp_DfM_May18-21_2015 Figure 2: Average temperature departure from mean during the stretch from May 18 to May 21, 2015.

Precipitation

The statewide average precipitation tallied 5.13 inches or 0.57 inches above normal (See Figures 3 & 4). May 2015 became the 35th wettest May among 143 years of statewide records. The rain fell quite regularly throughout the month as measurable precipitation fell on an average of 16.3 days for any single location. This was 39% more frequent than a typical May. Here’s a list of some of the stations that recorded at least 0.01” or more throughout the month:

Stations across central Iowa that recorded several days with measurable precipitation during the month of May 2015.

Stations across central Iowa that recorded several days with measurable precipitation during the month of May 2015.

Monthly rainfall totals ranged from 2.58 inches in Newton to 9.21 inches near Denison. Des Moines ended up 0.41 inches below normal for month even though the station recorded 16 days of measurable precipitation. Waterloo was 0.34 inches above normal for the month, while Mason City was 1.35 inches below its normal for May. The heaviest rainfall fell over west-central to southwest Iowa where 7 plus inches of rain was fairly common (See Figure 5). From the 23rd to the 27th, a statewide average precipitation of 1.56 inches was the wettest period throughout the month of May. Even with the persistent rainy pattern during the month, Iowa remained below normal precipitation for the year (See Figure 6).

may2015precipDFM Figure 3: Accumulated precipitation departure from mean for the month of May 2015.

may2015precipPOM Figure 4: Accumulated precipitation percent of mean for the month of May 2015.

iowa_mrms_q3_monthMay Figure 5: Radar estimated total precipitation throughout the month of May 2015.

Figure 6: Year-to-Date (ending May 31, 2015) accumulated precipitation departure from mean. Figure 6: Year-to-Date (ending May 31, 2015) accumulated precipitation departure from mean.

Several statistics were courtesy of Iowa State Climatologist Harry Hillaker:
http://www.iowaagriculture.gov/climatology/weatherSummaries/2015/pms201505.pdf

Blog post by Kenny Podrazik – NWS Des Moines

On This Date in Iowa Weather History: Six Foot Hail Drifts Occurred on August 6, 1890

On August 6, 1890, a very severe hail storm struck portions of Adair and Union counties producing incredible amounts of hail. One person wrote that near Orient “the hail destroyed all green vegetation and small animals, such as rabbits, ground squirrels, etc., and all the birds. It fell to a depth of four inches, varying in size from a quail’s egg to a hen’s egg, and drifting in many places to a depth of six feet, where it remained, when protected by the trash, for twenty-six days after the storm, or until September 1st.”

Another observer in Creston wrote that “hail commenced to fall…for forty minutes…on the bottomlands hail was drifted from four to six feet deep, and where protected by long grass, was found in large quantities twelve days after the date of the storm.”

Below are handwritten notes from the observer in Des Moines on August 6, 1890. Only pea size hail fell in Des Moines on that day, but they did mention the severe storm to the south and southeast.

August6-1890

From the bottom of the page after 6 reads: Falling barometer, stationary temperature, thunder heard at 1:45 pm. Loudest 2:20 pm. Rain began 2:10 pm, ended 2:30 pm. Hail size of peas 2:22-2:24 pm. Max wind 29 mph. Storm apparently more severe to the S and S.E.