Warmth and humidity fuel severe storms

■ Summer weather prevails with warmth and humidity entrenched for the Memorial Day weekend

■ Some patchy early-morning fog. Partly sunny skies. Warm and humid. Highs reach the middle 80s inland, but SE winds keep temperatures along the immediate lakeshore closer to 70.

■ Generally dry, but widely-scattered afternoon thunderstorms, affecting about 20-30 percent of the area, can’t be ruled out.

■ Partly cloudy, warm and humid overnight. Lows in the middle/upper 60s.

A warm and humid air mass invaded the Chicago area Saturday, triggering an outbreak of severe thunderstorms that brought hail, high winds, flooding rains, and even a tornado, primarily to the southern suburbs and northwest Indiana.

By early afternoon the National Weather Service had blanketed the area with a tornado watch and widespread severe thunderstorms quickly followed.

A tornado was reported near Minooka. The Joliet area was hard hit with 60 mph winds, hail, and torrential rains that produced flash flooding. Shorewood received 1.4 inches of rain in just 20 minutes, and the rain was even heavier in Hammond with more than two inches in 20 minutes.

The warm, humid weather should persist into Thursday, with periods of showers and thunderstorms expected, Memorial Day through Thursday.