Very warm and humid air will continue to expand northward across the MidwestSunday and Monday, causing many cities to crack the 90-degree mark for thefirst time this year.As the jet stream shifts into central Canada, steamy air will spread from thesouthern Plains into the Midwest on Sunday. Temperatures across much of theregion will soar 5 to 10 degrees above Saturday's highs.

For the first time this year, temperatures will reach or exceed 90 degrees inSt. Louis and Indianapolis. Des Moines will flirt with that mark.

Further warming, especially across the Upper Midwest, will send temperaturesinto the 90s as far north as Minneapolis and Wausau, Wis., on Monday.

The upcoming warmth will challenge record highs in some Midwestern cities andtowns. Madison, Wis., is one such location.

Higher humidity will add to the discomfort of the building warmth. Thoseplanning to spend some time outdoors playing sports or doing strenuous workshould have extra water handy.

The Midwest will not enjoy a quick end to the steamy conditions. Instead, theair will remain warm and humid into at least midweek.

Story by Senior Meteorologist Kristina Pydynowski