Heat and humidity that overtook the Twin Cities and much of Minnesota this week was at its worst Thursday, when it felt as hot as 108 degrees — though a break is coming over the weekend, the National Weather Service said.

But until cooler air arrives Saturday — think 80s and much lower humidity — sultry conditions will make it dangerous for anybody spending much time outside.

An excessive heat warning went into effect at noon Thursday for the Twin Cities metro area and much of south-central and southern Minnesota, including Mankato, Redwood Falls, Worthington, Marshall, Hutchinson and New Ulm.

"Extreme heat and humidity will significantly increase the potential for heat-related illnesses, particularly for those working or participating in outdoor activities," the Weather Service said. "Take care if you have to be outdoors today."

A heat advisory was posted for the remainder of southern Minnesota, south of a line from Morris to St. Cloud to Eau Claire, Wis. Willmar, Red Wing, Albert Lea and Rochester were included in the advisory, which was in effect until 8 p.m. Thursday.

Heat indexes — what it actually feels like outside — went above 100 degrees in many parts of the state. Minneapolis-St. Paul International Airport recorded a 103-degree heat index, while Blaine's went up to 107 degrees.

Thursday marked the fourth straight day of temperatures 90 degrees or warmer and the seventh time this month with 90-degree readings as the late-July heat wave continued.

The hot weather did little for farmers with parched fields and homeowners with brown lawns as drought conditions worsened. A report from the U.S. Drought Monitor issued Thursday showed much of Minnesota is experiencing a severe drought. Areas near St. Cloud, Rochester and Anoka County were placed in the "extreme drought" category.

All 87 counties in the state were identified as too dry, the report said.

However, the report measured conditions through Tuesday and did not factor in heavy rain that fell Tuesday night into Wednesday as storms raced across central Minnesota.

The storms dropped 1 to 4 inches of rain from Willmar to the Twin Cities, toppling trees, downing power lines and ruining some structures. Damage was particularly heavy in New London, Minn., near Willmar. In Hudson, Wis., a Tuesday storm ripped a roof off an apartment building.

Canby, Minn., appeared to have been the hottest place in Minnesota on Wednesday with a high of 102 degrees. The Lac Qui Parle Airport also reached 100 degrees, the Weather Service said. The Twin Cities hit a high of 93 degrees.

Strong and possibly severe storms Thursday night into Friday will usher cooler and drier air into Minnesota. By Saturday, temperatures in the metro will be down to the low 80s, the Weather Service said.