Preliminary Weather Summary

Written by Theresa Rose on May 19, 2020

Provided by Justin Glisan, Ph.D., State Climatologist, Iowa Department of Agriculture and Land Stewardship

Unseasonably cool conditions persisted across Iowa during the reporting period, though temperatures were not as cold as last week. Temperatures were generally four to eight degrees below normal with the statewide average temperature of 54.4 degrees, 6.1 degrees below normal. In a welcome change, wetter than normal conditions returned across much of Iowa with near to below normal conditions reported in pockets of western Iowa. Southeastern Iowa reported the wettest conditions with positive departures of up to three inches.

Cloud cover remained as spotty showers formed on the backside of a low pressure system moving east through northern Illinois on Sunday (10th) afternoon. Gusty northwest winds slowed down as daytime highs remained colder than average, in the mid 40s north to mid 50s south. Cloudy conditions persisted into Monday (11th) with overnight lows remaining in the upper 30s and low 40s. Skies began to clear towards late afternoon and evening as a weak cold front dropped south across Iowa. With a light north wind, morning temperatures on Tuesday (12th) were unseasonably cold with lows across eastern Iowa in the mid to upper 20s. Cloud cover in western Iowa held temperatures in the low 40s with the statewide average at 35 degrees, 12 degrees below normal. Conditions through the day began to warm as partly sunny skies were observed across much of the state. Highs reached into the upper 50s and low 60s, though still six to 16 degrees below normal. A small disturbance moved through Iowa during the afternoon and evening hours on Wednesday (13th) bringing showers and thunderstorms. Rain totals from this system were highest across northern and eastern Iowa. Daytime highs remained in the mid to upper 50s.

A warm front lifted across southern Iowa overnight into Thursday (14th) in advance of a strong low pressure center, forcing additional showers and thunderstorms in southern Iowa. Additional storms, some strong to severe, formed during the evening hours across central Iowa with multiple reports of hail and straight-line winds; a 3.00-inch-sized hail stone was reported in New Virginia (Warren County). Moderate to heavy rain fell across southeastern Iowa as thunderstorms slowly moved over the same areas. Two-day rainfall totals at 7:00 am on Friday (15th) showed nearly 40 stations reporting over two inches; half of the state’s rain gauges observed at least 0.63 inch with a statewide average rainfall of 0.84 inch. Ottumwa Industrial Airport (Wapello County) reported 4.43 inches, breaking its rainfall record for the date as well as tying its existing May daily record set in 1993. High pressure dominated during the rest of the day with overnight lows into Saturday (16th) remaining in the 50s under generally clear skies. A broad system of showers and thunderstorms entered western Iowa and propagated through the state during the early evening and overnight hours. Measurable totals were reported statewide with a concentrated rain band along the low’s attendant cold front bringing at least 0.50 inch to much of Iowa’s western two-thirds. The heaviest amounts fell across northern Iowa, where the low slowly spun before exiting the state into Sunday (17th) morning; Mason City (Cerro Gordo County) reported 2.25 inches while Ringsted (Emmet County) observed 2.43 inches. The statewide average rain total was 0.86 inch.

Weekly rain totals ranged from 0.16 inch in Sioux City (Woodbury County) to 5.14 inches at Ottumwa Industrial Airport (Wapello County). The statewide weekly average precipitation was 1.71 inches while the normal is 1.05 inches. Donnellson (Lee County) and Lamoni (Decatur) reported the week’s high temperature of 81 degrees on the 14th, on average nine degrees above normal. Stanley (Buchanan County) reported the week’s low temperature of 24 degrees on the 12th, 22 degrees below normal.