IOWA MONTHLY WEATHER SUMMARY – APRIL 2020
Temperatures averaged 46.8 degrees or 2.1 degrees below normal while precipitation totaled 1.59 inches or 1.92 inches below normal. April 2020 ranks as the 40th coldest and 17th driest April in 148 years of statewide records. A colder and drier April last occurred in 2018, which was the coldest April on record.
Negative temperature departures were reported statewide for the month of April with eastern Iowa observing up to four degrees below normal. There were seventeen days in which the statewide average temperature was below normal with a significant cold snap from the 12th through the 17th. Average temperatures were at least 15 degrees colder than average over that stretch of days. Daytime highs on the 15th were unseasonably cold at 40 degrees, 20 degrees below average. Temperatures recovered over the last 10 days of the month with seven days of above normal warmth.
April’s statewide average maximum temperature was 59.3 degrees, 1.3 degrees below normal while the average minimum temperature was 34.3 degrees, 3.0 degrees below normal. Red Oak (Montgomery County) and Shenandoah (Page County) reported the month’s high temperature of 87 degrees on the 7th, on average 26 degrees above normal. Estherville Municipal Airport (Emmet County) reported the month’s low temperature of 6 degrees on the 15th, 29 degrees below normal.
Heating Degree Days
Home heating requirements, as estimated by heating degree day totals, averaged 14% more than last April and 15% more than normal. Heating degree day totals are running 11% more than last year at this time and 3% less than normal.
While measurable rain and snow fell across Iowa during April, a majority of the National Weather Service coop stations reported below average precipitation totals. The driest part of the state was located across a band stretching from western Iowa into north-central Iowa, where precipitation deficits were between 2.50 – 3.00 inches.
April started wet as showers and a few thunderstorms formed across northwestern Iowa on the 1st. The complex moved through central and eastern Iowa before dissipating in the early afternoon hours. Gusty southerly winds continued through the day as a warm front lifted north across Iowa. An area of showers formed across south-central Iowa in the afternoon and moved northeast in advance of a cold front across western Iowa. Two-day rain totals were generally under 0.20 inch, although Ottumwa Industrial Airport (Wapello County) and Lamoni Municipal Airport (Decatur County) reported totals of 0.71 inch and 0.48 inch, respectively. Winter weather returned on the 3rd as another low pushed through Iowa. Northwest Iowa reported light snow and freezing rain with a transition across central Iowa. Southeastern Iowa reported all rainfall, as it was on the warmer side of the system. Measurable precipitation fell across most of Iowa with the highest totals in south-central Iowa; general amounts were below 0.75 inch with Columbia (Marion County) reporting 0.80 inch. Snow totals ranged from a trace amount at multiple northwestern stations to 1.0 inch in Forest City (Winnebago County).
Isolated showers and a few thunderstorms popped up in central and eastern Iowa on the 6th but dissipated in the evening. Rainfall amounts at 7:00 am on the 7th were light, though Lowden (Cedar County) reported a 0.64-inch total. A cold front swept through the state on the 8th bringing rain to northern Iowa. Rain totals of around a few tenths of an inch were reported in Iowa’s eastern quarter. Heavier amounts were observed in a handful of northeastern counties; Cresco (Howard County) reported 0.40 inch while Decorah (Winneshiek County) reported 0.42 inch. Light showers pushed through western Iowa during the morning hours on the 11th and reformed into the afternoon. Showers and thunderstorms continued to pop up over portions of southern Iowa during the evening, persisting overnight. Rain totals varied from lighter amounts in western Iowa to near 0.50 inch in portions of eastern Iowa. The broad area of low pressure continued to push through with several waves of showers and thunderstorms bringing measurable rainfall statewide. The highest totals were observed along a narrow band stretching from Dallas County northeast to Winneshiek County. Nearly 50 rain gauges had totals at or above one inch with a report of 1.75 inches in Des Moines (Polk County). Totals east and west of the band were generally under 0.50 inch with the statewide average of 0.55 inch.
A substantial snowstorm impacted southern Iowa from late on the 16th through the 17th with measurable snow generally south of Interstate 80. The highest accumulations were reported near the Iowa-Missouri border, where snowfall rates approached one to two inches per hour. Clarinda (Page County) observed 8.0 inches while across the state Keosauqua (Lee County) reported 7.0 inches. South-central Iowa received the highest totals with Ringgold County stations in Beaconsfield and Mount Ayr reporting 12 inches; Allerton (Wayne County) reported 13 inches. Accumulations dropped off into central Iowa with general totals between three to six inches. Spotty showers formed in western Iowa after sunset and continued to cross the state through the 24th. A secondary disturbance moving through Missouri also brought measurable rainfall across southern Iowa. This complex slowly pushed out of southeastern Iowa early on the 25th. Rain totals were highest across Iowa’s southern two tier of counties, where slower cells produced heavier rain. Randolph (Fremont County) reported 0.70 inch while Keokuk Municipal Airport (Lee County) reported 1.12 inches; Corning (Adams County) reported 1.98 inches.
Cloud cover increased into the early morning hours of the 27th as a line of showers and some thunderstorms moved into western Iowa. The line remained somewhat organized, though dissipated as it moved through central Iowa into the early afternoon hours; light showers reformed in eastern Iowa during the evening hours with rain totals for the day generally under a few tenths of an inch across southwestern Iowa; Mount Ayr (Ringgold County) reported 0.42 inch. Clouds were increasing in advance of a low pressure system that propagated across Iowa through the day on the 28th. Measurable totals were reported across much of Iowa with the highest amounts in the northwest as well as in east-central Iowa. DeWitt (Clinton County) reported 0.67 inch while Primghar (O’Brien County) observed 0.60 inch; totals at remaining stations were generally under a few tenths of an inch. Additional light showers formed on the backside of the low as it moved out of eastern Iowa.
Monthly precipitation totals ranged from 0.51 inch in Denison (Crawford County) to 4.34 inches in Lamoni (Decatur County). Portions of Iowa reported above normal snowfall, especially across south-central Iowa, with the preliminary average statewide total of 3.7 inches, 2.1inches above average. This ranks as the 13th snowiest April on record. Allerton (Wayne County) reported the highest total of 13.6 inches.
April was relatively quiet in terms of severe weather with only two days of storm reports from warned thunderstorms. The first event occurred during the evening and nighttime hours on April 7th. Several discrete severe thunderstorms popped up in eastern Iowa leading to multiple reports of hail ranging in size from nickels to ping-pong balls; some vehicle damage was reported with many of the reports occurring across eight counties. A cold front swept through Iowa on the 8th producing a few severe thunderstorms that raced through southeastern Iowa during late afternoon. Hail up to the size of golf balls was reported in Lowell (Henry County).
Justin Glisan, Ph.D.
State Climatologist of Iowa
Iowa Dept. of Agriculture & Land Stewardship
Wallace State Office Bldg.
Des Moines, IA 50319
Telephone: (515) 281-8981
WEATHER BY DISTRICTS
|WEATHER BY DISTRICTS|
|TEMPERATURE (F)||HEATING DEGREE DAYS||PRECIPITATION (inches)|
|April 2020||April 2020||Since Jul., 1, 2019||April 2020||Since Jan.1, 2020||Apr 2020|
|* Departures are computed from 1981-2010 normals.|
|The weather data in this report are based upon information collected by the U. S. Dept. of Commerce, NOAA National Weather Service.|