Hey Minnesota, welcome to your sweaty fall

The Mississippi River
Bare trees are reflected in the Mississippi river as fallen leafs float on Sunday, Oct. 19, 2014.
Bridget Bennett | MPR News 2014

Updated 3:25 pm. | Posted 12:35 p.m.

Autumn comes Friday afternoon in Minnesota, but the weather will be less about sweaters — and more about sweat.

National Weather Service forecasters, who posted a heat advisory for Friday afternoon, say the heat index could hit 100 degrees in St. Cloud, Minn., and the Twin Cities on Friday when fall officially arrives here at 3:02 p.m.

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The hot forecast is leading the Twin Cities weather service office to caution people planning outdoor activities to take care. Much of southern Minnesota will be steamy.

That's a startling map, but the National Weather Service on Thursday was just getting warmed up.

The agency also said low temperatures in the Twin Cities will top 70 degrees for the next three nights, which would be a record for latest consecutive 70 degree lows this late in the year.

On top of that, the National Weather Service Climate Prediction Center reports that its October through December outlook favors warmer-than-normal weather for Minnesota and Wisconsin.

That's a bad sign for people hoping to walk the Apostle Islands ice caves this winter.

On the flipside, shorts and sandals should be OK for a fall color foliage walk in the woods this weekend.