Thunderstorms were scattered through the Rockies and over the Plains on Wednesday, and temperatures topped 100 degrees in the Southwest.
Moist, unstable air flowing northward across the Plains threatened to fuel more strong thunderstorms, the National Weather Service said.
Earlier in the day, hail piled up about 4 inches deep southeast of Lander, Wyo.
A cluster of thunderstorms slowly weakened as it drifted across sections of the upper Mississippi Valley.
In Iowa, a tornado briefly touched down south of Clarion but caused no damage. High wind damaged a grain bin near Ayrshire and snapped a flag pole near Emmetsburg. Hail as big as golf balls fell near Webb.
Elsewhere, showers and thunderstorms were scattered across the Florida Peninsula and were widely scattered along the Atlantic and Gulf coasts and the southern Plains.
Heavier rainfall amounts for the six hours up to 2 p.m. EDT were 0.58 of an inch at Waterloo, Iowa, and 0.52 of an inch at Williston, N.D.
Hot, humid air surging northward through the lower Mississippi Valley into the central Plains boosted temperatures to or above 90, accompanied by strong southerly wind blowing from northern Texas into much of Oklahoma, Kansas and southeastern Nebraska.
Temperatures in the desert Southwest soared above 100. On Tuesday, a 2-year-old boy who wandered away from his home in 112-degree heat in a desert subdivision of Phoenix apparently died of exposure to the sun, officials said Wednesday.