The statewide average temperature for the month of April 2015 was 50.8°F which was 1.9°F above normal (See Figures 1 and 2). April 2015 now ranks as 38th warmest out of 143 years of records. Well above normal temperatures affected the state on the 1st of the month, placing high temperatures across the western two-thirds of Iowa into the 80s (See Figure 3). Temperatures throughout the rest of the month were up-and-down resulting in near normal temperatures (See Figures 4 & 5). Hence, the very warm first of the month added at least an additional 0.5°F onto the monthly average for April (See Figure 6). A brief cold snap occurred on the 3rd and 4th with another extended cold snap lasting from the 20th to the 27th. In between these two cold snaps were a couple of weeks of near to slightly above normal temperatures for central Iowa. During the second cold snap, several locations received a hard freeze on the 22nd and 23rd when low temperatures dropped into the 20s. The warmest temperature in April for the state was 88°F in Little Sioux on the 1st and then 3 days later on the 4th, the coldest temperature in Iowa of 19°F occurred in Elkader and Belle Plaine, Iowa. The most significant temperature gradient across the state set up on April 9th, when highs rose into the middle 80s over southeast Iowa and the northwest portion of the state remained in the lower 40s (See Figures 7 & 8).
Figure 1: Iowa average temperature for April 2015.
Figure 2: Iowa average temperature departure from mean for April 2015.
Figure 3: April 1, 2015 average temperature departure from normal.
Figure 4: Temperature trend graph for Des Moines during April 2015 shows the wide range of temperatures throughout the month.
Figure 5: Temperature trend graph for Waterloo during April 2015 shows the wide range of temperatures throughout the month.
Figure 6: Average temperature departure from mean from April 2 to 30, 2015. Compared to Figure 1, April 1st resulted in a significant increase in the monthly average temperature.
Figure 7: Average maximum temperature on April 9, 2015 ranged in the lower to middle 80s in southeast Iowa to the lower 40s over the northwest.
Figure 8: Average maximum temperature departure from mean on April 9, 2015 showed the sharp gradient in temperatures across Iowa.
The statewide average precipitation totaled 3.39 inches which was 0.12 inches above normal (See Figures 9 & 10). This resulted in the 49th wettest April among 143 years of statewide climatological records. The highest monthly total at any location was 6.88 inches in Lake Mills, Iowa while the lowest monthly total was 1.18 inches at Rock Valley. The most active periods for precipitation were from the 7th and 9th, from the 18th to 20th, and 24th to 25th. There were a few severe weather events throughout the month, with the most significant event occurring on the 9th when two tornadoes touched down in east-central Iowa. In fact, the 9th had a multitude of different weather; from fog in the morning to severe weather in the southeast to snow over the northwest portions of the state (See Figure 11). In Schleswig, Iowa, 4 inches of snow was reported as a band of 1 to 4 inches set up of west-central to northwest Iowa (See Figure 12). Additional severe weather events materialized on the 7th, 8th, and 18th of the month over portions of southern Iowa.
The statewide average snowfall was just 0.3 inches for the month while the normal for April is 1.6 inches. The seasonal snowfall total now sits at 26.6 inches which is 5.6 inches below the average. April 2015 ranks as the 47th lowest seasonal snowfall total among 128 years of snowfall records for the state. In fact, there have been only 4 years (since snowfall records began at Des Moines in 1884) when Des Moines recorded no measurable snow (greater than a trace) during the entire months of March and April. The 4 years include 1889, 1908, 1981, and 2015. Des Moines last trace of snow in 2015 occurred on March 5.
Figure 9: Accumulated precipitation for the month of April 2015.
Figure 10: Accumulated precipitation departure from normal during April 2015.
Figure 11: This graphic shows the various weather across Iowa on April 9, 2015.
Figure 12: Visible satellite imagery showing the 1 to 4 inch snow band that fell over west-central to north-central Iowa on April 9, 2015.
Visible Satellite image on April 9, 2015 depicts the ling of strong to severe thunderstorms developing over southeast Iowa and northern Missouri.
The statewide statistics and a few other statistics were courtesy of Iowa State Climatologist Harry Hillaker and you can find a more extensive statewide summary here: http://www.iowaagriculture.gov/climatology/weatherSummaries/2015/pms201504.pdf
Blog post by Kenny Podrazik – NWS Des Moines