UPDATED 06/21/11 7:37 p.m.

CHICAGO (STMW) — Severe thunderstorms are on the way following a steamy first day of summer in the Chicago area, and they could stick around throughout the week.

The National Weather Service has issued a severe thunderstorm watch for several Illinois counties, including Cook, DuPage, Kane, Kankakee, Lake, Kendall and McHenry.

The watch, in effect until 1 a.m. on Wednesday, also includes Lake, Porter, Newton and Jasper counties in Indiana.

And the weather service has also issued a tornado warning until 8 p.m. for southeastern LaSalle County and northwestern Livingston County. Doppler radar indicated a severe thunderstorm capable of producing a tornado was spotted near Minonk, which is about 16 miles southwest of Streator and moving northeast at 30 mph.

There’s a 70 percent chance of thunderstorms Tuesday night, and then a lesser chance every day this week, the National Weather Service said.

On the first day of summer, Midway Airport recorded a high of 88 degrees just before 4 p.m. But the heat index, what the temperature actually feels like, was a balmy 94 degrees. Relative humidity was recorded at 57 percent.

Scattered thunderstorms will hit north central Illinois, northeast Illinois and northwest Indiana on Tuesday night with a few of the stronger storms capable of producing damaging winds, large hail and frequent lightning, the weather service said.

The storms will move quickly across the area, the weather service says, with the possibility of brief heavy downpours.

That will lead to some localized flooding, especially because portions of the Kankakee and Illinois rivers are already near or above flood stage.

And where’s the sun in that rainy forecast? Out of sight until Saturday, when the area should reach a more comfortable 70 degrees.
Temperatures will fall through the week, with a high of 76 on Wednesday, 68 on Thursday, and 72 on Friday.

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