Another Midwestern Heat Wave Breaks Temperature Records

High heat and low humidity were present this week across the Midwest. Many stations hit triple digits for the first time in nearly a decade. Minnesota, Iowa, and Missouri were the warmest with temperature departures ranging from 6 to greater than 10°F above normal (Figure 1). Watonwan County, Minnesota, recorded an average temperature of 80.2°F (10.4°F above normal). Their single-day maximum temperature of 102°F occurred on June 21. Less extreme average temperature departures were observed in Illinois, Indiana, Ohio, Kentucky, and Michigan. Maximum temperatures were warmest in Minnesota and Iowa where departures ranged from 6-10°F above normal (Figure 2). As of June 21, most stations across the Midwest had greater than 5 consecutive days where the maximum temperature was greater than or equal to 90°F. Minimum temperatures followed similar patterns for the week (Figure 3). There were 403 high maximum and 597 high minimum temperature records broken or tied across the Midwest this week (Figure 4). Despite the high heat, there were a couple of temperature swings which allowed for cooler temperatures across the Midwest. In fact, Akron-Canton and Youngstown-Warren, in Ohio, both tied daily minimum temperature records on June 19.

Drier Week for Most, Isolated Heavy Rain for Some

Southern Missouri, central Indiana and western Ohio missed out on precipitation this week (Figure 5). As of June 21, many stations in these locations were within the top 10 driest for the previous two weeks (Figure 6). Most of the Midwest had well below-normal precipitation (Figure 7). A large portion of the Ohio River Valley received less than 75 percent of normal precipitation. Springfield WBO, Missouri, had a streak of 11 days (as of June 21) without measurable precipitation (>0.01 inches). The record streak was 25 days set from August 23 – September 16, 2017. Not everywhere was dry, though. Thunderstorms in Iowa, Wisconsin, and Minnesota allowed for heavier precipitation totals ranging from 0.75-1.5 inches (isolated 2.0-inch totals). River and stream gauges showed below-normal flows in central Illinois, Indiana, and Kentucky. The rest of the Midwest appeared to be near normal, with isolated above-normal flows where heavy rainfall occurred (Figure 8).

Severe Storm Reports

There were 12 tornado, 49 hail, 701 wind, and 35 high wind storm reports this week (Figure 9).

June 15 Eleven preliminary tornado reports occurred in Wisconsin. The La Crosse, Wisconsin, and Green Bay, Wisconsin, National Weather Service confirmed 12 tornadoes (2 EF-2 and 10 EF-1). No injuries or deaths were reported, but extensive structural, tree, and power pole damage was observed. Hail measuring 2.75 inches in diameter was reported in Buchanan County, Iowa. An 80-mph wind gust was measured in Marquette County, Wisconsin.

June 16 The largest hail report of 1.75 inches in diameter occurred in Geauga and Stark Counties in Ohio. There were 124 wind reports in Illinois, Michigan, Missouri, Ohio, and Kentucky. A 74-mph wind gust in Monroe County, Missouri was measured by the Missouri Mesonet.

June 17 There were 131 wind reports across Illinois, Indiana, Kentucky, and Ohio. A 72-mph wind gust was measured in Rowan County, Kentucky. Damage to buildings, trees, and power poles were reported.

June 20 There were two tornado reports in Minnesota (EF-1 in Redwood County and an EF-0 in Brown County). There were 9 hail reports in excess of 1.0 inch in Minnesota and 97 wind reports throughout Minnesota, Wisconsin, and Michigan. One fatality in Douglas County, Minnesota, resulted from a tree falling on a camper.

Drought Expansion

The June 21 US Drought Monitor showed an expansion of abnormally dry (D0) conditions in Illinois, Missouri, Kentucky, and Indiana. Moderate drought (D1) was introduced to east-central Illinois, west-central Indiana, and central Kentucky (Figure 10). From the previous week’s map, the land in D0-exceptional drought (D4) increased by 15.33%. In Indiana and Kentucky, there were reports of late-planted crops showing symptoms of drought stress and lawns going dormant due to dry conditions.