Iowa Preliminary Weather SummaryWritten by Theresa Rose on June 30, 2020
Provided by Justin Glisan, Ph.D., State Climatologist Iowa Department of Agriculture and Land Stewardship
In a shift from recent weeks, cooler than normal temperatures were felt across much of Iowa with up to three degrees below average departures in eastern Iowa. The statewide average temperature was 71.2 degrees, 1.6 degrees below normal. A continued active storm track brought thunderstorms through Iowa over several days with above average rainfall reported across eastern Iowa. Positive departures of up to 3.00 inches were found in the northeast, while western Iowa observed deficits of up to an inch.
Thunderstorms began popping up across eastern Iowa during the afternoon on Sunday (21st) ahead of a strong disturbance that produced some severe thunderstorms across northern Iowa over the evening hours. There were several reports of one-inch hail and severe straight-line winds in excess of 60 mph; Sheldon (O’Brien County) reported a 62 mph wind gust. Further development occurred in the early morning hours as the complex over eastern Iowa consolidated, bringing locally heavy downpours and strong wind gusts. Additional storms, some severe, formed in southern and central Iowa through Monday (22nd) morning and moved east as another round fired in west-central Iowa. Though daytime highs remained in the low to mid 70s, muggy conditions supported thunderstorm activity. A cold front finally cleared Iowa overnight into Tuesday (23rd) with two-day rain totals at 7 a.m. showing the highest amounts in eastern Iowa, where flash flood warnings were in place. All Iowa stations reported measurable rainfall with much of Iowa’s northeast quadrant observing totals above 1.50 inches. Nearly 70 stations reported totals over 2.00 inches with a statewide average rainfall of 1.17 inches; Clutier (Tama County) reported 5.17 inches. Partly cloudy skies and northwesterly winds remained through the day with highs in the upper 70s southwest to upper 60s northeast.
Skies cleared into early Wednesday (24th) though partly cloudy conditions were reported across central Iowa through the afternoon and evening hours with a light, variable wind. Isolated thundershowers formed in eastern Iowa on the backside of a low pressure center. Only a handful of stations reported rain with Fayette (Fayette County) observing 0.60 inch. Clear skies and southerly winds helped push temperatures into the mid to upper 80s on Thursday (25th). Overnight lows dropped into the low 70s across southern Iowa while clouds and thunderstorms pushed through northern Iowa, keeping temperatures in the mid to upper 60s. Early on Friday (26th), waves of showers and thunderstorms propagated across the state ahead of a low pressure center. Some severe storms moved through eastern Iowa into the evening hours, while overnight into Saturday (27th) a sluggish boundary draped over southern Iowa re-fired slow-moving storms.
Higher rainfall totals were reported in southeastern Iowa with totals generally between a few tenths of an inch to over two inches; Washington (Washington County) observed 2.21 inches. High temperatures peaked into the low to mid 80s with spotty thunderstorms across east-central Iowa. Overnight lows remained in the mid to upper 60s as an arc of thunderstorms pushed into southwestern Iowa with a trailing shield of showers. Totals reported at 7 a.m. on Sunday (28th) across Iowa’s southern half ranged from a few tenths in the southwest tailing off farther east. Williamsburg (Iowa County) reported 0.93 inch after multiple storms passed over the station.
Weekly precipitation totals ranged 0.02 inch at Atlantic Municipal Airport (Cass County) to 5.40 inches at Clutier and Elkader (Clayton County). The statewide weekly average precipitation was 1.61 inches while the normal is 1.17 inches. Keokuk Lock and Dam (Lee County) reported the week’s high temperature of 92 degrees on the 26th, six degrees above normal. Multiple stations reported the week’s low temperature of 50 degrees on the 24th, on average 10 degrees below normal.