Temperatures
For March 2015, the statewide average temperature for Iowa was 36.8°F which was 0.9°F above normal and becomes the 53rd warmest March on record out of 143 years of statewide climatological records (See Figure 1). In fact, a sharp gradient set up across Iowa for the month of March where the northwest ended up being 2°F below normal while the far eastern edges of the state averaged 5°F above normal (See Figure 2). A temperature swing from -17°F to 90°F was the 4th largest temperature extreme for the state. The 3 prior Marches with larger temperature swings were in 1943, 1959, and 1962.
The very cold stretch to end February continued into the first week of March with the first 6 days below normal for the state (See Figure 3). Northern and eastern portions of Iowa recorded minimum temperatures below zero, at least once, during the aforementioned stretch. The coldest day of the month came on the 5th (See Figure 4). For stations within the Des Moines CWA (County Warning Area), the coldest maximum temperature on the 5th was 11°F at Waterloo while the lowest temperature was -14°F at Grundy Center. However, for much of the state, minimum temperatures were 25 to 30 degrees below normal on March 5th (See Figure 5). For the state, the coldest temperature of the month was -17°F on the 5th in Stanley (Buchanan County). Temperatures quickly rebounded across Iowa beginning on the 7th and the warm or above normal pattern persisted through the 22nd. The hottest day of the month occurred on the 16th when much of the state rose well into the 70s and 80s for maximum temperatures (See Figure 6). Des Moines International Airport topped out at 84°F but the hottest temperature on the 16th was 90°F in Sioux City, Iowa. In fact, this is the earliest 90°F temperature reading (calendar year) in Iowa, shattering the previous record by 6 days. The old record was 92°F at Clarinda on March 22, 1910. The second cold snap occurred from the 23rd through the 28th (See Figure 7), even though northeast Iowa was below normal for average temperatures on the 22nd, the statewide average ended up just above normal for the 22nd. The last couple days of March warmed back to above normal to end the month.
Figure 1: Average temperature across Iowa for March 2015.
Figure 2: Average temperature departure from mean in Iowa for March 2015.
Figure 3: Average temperature departure from mean from March 1 to March 6, 2015.
Figure 4: Average minimum temperature for March 5, 2015.
Figure 5: Average minimum temperature departure from mean for March 2015.
Figure 6: Average maximum temperature across Iowa for March 2015.
Figure 7: Average temperature departure from mean from March 23 to 28, 2015.
Precipitation
A very dry March for Iowa in 2015 as the statewide average precipitation was a mere 0.59 inches or 1.56 inches below normal (See Figures 8 and 9). March 2015 becomes the 7th driest March out of 143 years of statewide records. If fact, much of the region remained dry and recorded top 10 driest Marches on record (See Figure 10). The statewide average snowfall was 0.9 inches which is 3.8 inches below normal (4.7 inches) for March. Not since 1994 that Iowa had a lower statewide average snowfall for the month of March and 2015 now ranks 9th lowest among 128 years of snowfall records.
Some light snow flurries or snow showers periodically fell over portions of the state between the 1st and the 4th, but the bulk of what little precipitation that did accumulate occurred between the 22nd and 24th of the month. A very dry period from March 4th to March 21st occurred across the state. During this time frame, the statewide average precipitation was only 0.01 inches (See Figure 11) resulting in some fire weather concerns during the middle of the month when temperatures were well above normal. In fact, Des Moines and Waterloo crept into the top 10 driest Marches for their respective stations (See Tables 1 and 2). Precipitation fell in the form of snow or freezing rain across portions of north-central to northeast Iowa as several shortwaves tracked over this area between the 22nd and 24th. Widespread heavy rain fell over the state on the 24th (See Figure 12). The highest amount was 1.32 inches in New Market (Taylor County) and the highest snowfall amount was 12.5 eight miles east-northeast of Decorah on the 22nd.
Figure 8: Average accumulated precipitation departure from mean from March 2015.
Figure 9: Accumulated precipitation March 2015.
Figure 10: March 2015 precipitation total ranks by Climate District. Image is Courtesy of Iowa Environmental Mesonet.
Figure 11: March 4 to 21, 2015 accumulated precipitation shows how sparse precipitation was during the middle portion of the month.
Figure 12: March 21, 2015 observed precipitation was the most widespread rainfall for the month.
Table 1: Top 10 Driest Marches for Des Moines, Iowa since 1878. 2015 ranks 10th driest March.
Table 2: Top 10 Driest Marches for Waterloo, Iowa since 1895. 2015 ranks 9th overall driest.
Statewide climate statistics are courtesy of Iowa State Climatologist Harry Hillaker: http://www.iowaagriculture.gov/climatology/weatherSummaries/2015/pms201503.pdf
Blog post by Kenny Podrazik – NWS Des Moines
A Very Dry March 2015 http://t.co/9bwsNE96e3