Iowa Weekly Growing Season Report
Preliminary weather summary for the week May 11-17, 2026
A significant shift in the large-scale pattern brought an active end to the reporting period, as several rounds of severe thunderstorms produced large hail, high winds and a weak tornado in Iowa. Rainfall was also above normal across portions of southern and northeastern Iowa. Unseasonably warm temperatures continued statewide with the highest departures approaching five degrees; the statewide average temperature was 63.8 degrees, 4.6 degrees above normal.
Sunday (10th) afternoon was breezy with northwesterly winds, mostly sunny skies and daytime highs in the upper 60s and low 70s. Winds became variable and light into Monday (11th) with morning lows in the low 30s north to low 50s south. A shift to southerly winds pushed afternoon highs into the low 80s southwest while temperatures were 15-20 degrees cooler farther northeast. A weak cold front began dropping through the state before daybreak on Tuesday (12th), bringing light showers over portions of northern Iowa, though totals were below 0.10 inch over northern Iowa at 7:00 am. Showers became more numerous as the front pushed through eastern Iowa with 0.12 inch reported in Bellevue (Dubuque County) and 0.13 inch in Iowa Falls (Hardin County). Afternoon conditions stabilized as high pressure took control of the Upper Midwest. Temperatures rose into the upper 70s with spotty low 80s and anomalously low dewpoints over northern Iowa. Strong northwesterly winds also lofted dry, cultivated soil into the air, reducing visibility at several locations. Starry skies prevailed into Wednesday (13th) with unseasonably warm morning lows in the mid 50s southeast; temperatures were more seasonal across northern Iowa. The rest of the day was pleasant with temperatures in the 70s and blustery northerly winds.
Thursday (14th) started with clear skies and temperatures in the 50s across Iowa’s western two-thirds. Cloud cover increased over western and northern Iowa as stronger southerly winds built in. Afternoon temperatures held in the 70s as isolated thunderstorms formed along the Iowa-Minnesota border. Additional showers formed over northeastern Iowa through the late evening hours, pushing into the southeast corner after sunset. Several stations in Lee County observed higher totals ranging from 0.29 inch in Salem to 0.45 inch in Augusta; many stations in the northeast one-third of the state picked up measurable totals. Friday (15th) was the first of several severe weather days across the Midwest as daytime temperatures quickly warmed into the upper 80s in the presence of ample northerly moisture advection. A strong cold front slammed into this unstable airmass through the evening hours, firing strong to severe thunderstorms along the boundary. Northwestern Iowa experienced widespread reports of damaging hail, some of which were larger than two inches, as was observed in Anthon (Woodbury County) and several stations in Hancock County, including Kanawha and Meservey. Severe straight-line winds were also reported in southwest and northeast Iowa. Rainfall was widespread with more than half of the stations measuring at least 0.30 inch; Allison (Butler County) registered 1.40 inches. Saturday (16th) saw more concentrated severe weather in the southwest with 2.75-inch hail reported in Red Oak (Montgomery County) and a weak tornado near Gravity (Taylor County). Heavy rain also overspread much of south Iowa along with pockets in the northwest; nearly 20 stations had at least 2.00 inches with an additional 30 hitting 1.00 inch or more.
Weekly precipitation totals ranged from 0.10 inch at Sioux City Air National Guard Base (Woodbury County) to 6.08 inches in Westfield (Plymouth County). The statewide weekly average precipitation was 0.96 inch; the normal is 1.10 inches. Sioux City Airport (Woodbury County) reported the week’s high temperature of 95 degrees on the 15th, 23 degrees above normal. Spencer Municipal Airport (Clay County) reported the week’s low temperature of 26 degrees on the 11th, 20 degrees below normal. Four-inch soil temperatures were in the low to mid 60s statewide as of Sunday.
