The second wave of cool autumn air to descend on the Northland this season is set to arrive this morning, with temperatures forecast to drop into the mid-20s in many areas away from Lake Superior.
International Falls, Hibbing, Ely and much of the Arrowhead are expected to get temperatures far enough below 32 degrees that unprotected crops and plants are likely to get nipped hard, according to the National Weather Service in Duluth.
The Weather Service has issued a freeze warning for most of Northeastern Minnesota, from Carlton County north, and a frost advisory for areas to the south as well as Douglas and Burnett counties in Wisconsin.
A freeze warning is issued when temperatures are expected to drop to 28 degrees or colder for the first time in a season. A frost advisory is for temperatures down to about 32 degrees.
The Twin Ports proper, North Shore and other areas within about 10 to 15 miles of Lake Superior should be spared from any killing frost, with low temperatures in the mid-30s.
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Several areas from the Iron Range north, away from Lake Superior, experienced some frost last week when morning lows dropped to 32 and below on Thursday, Friday and Saturday. Embarrass dropped to 28 degrees.
The frosts so far are coming right on time. Cook has Minnesota's earliest first frost, on average, on Sept. 10. That's followed in the region by Hibbing on Sep. 14, Virginia on Sept. 15 and International Falls on Sept. 17. Duluth International Airport on average sees its first frost Sept. 23, but the relatively warm waters of Lake Superior keep the first frost at bay in the harbor until Oct. 18.
This will be the coolest week in many months in the Northland, with forecast highs only in the 50s. Highs should return to the more-seasonal 60s by Sunday. The last time Duluth saw a week with highs mostly in the 50s was in April.
Sunday was the 106th day this year in Duluth when the high temperature hit at least 70 degrees. That ties a record, set in 1955, for the most 70-degree days in the city's recorded history.
Despite light rain Sunday night, the region continues to plunge toward an official drought. Much of the Northland remains 4 inches or more below normal for rainfall since the June flood. Duluth already is about 2 inches below normal just for September.
