This morning's discussion (2:46) from the NWS Duluth mentions that the coldest air will pivot over northern Wisconsin tonight - potentially there will be colder temperatures tonight.
The forecast for me last night was about -8 and I had -9.3, while the forecast for me tonight (above) is -20.
I measured 17.6 inches of snow pack in my yard this morning, I believe this snow contributed with radiational cooling last night.
The birds must be cold!
Chickadees, Nuthatches, and Grey Squirrels have been attacking the bird seed this morning. This picture (to the right) is of a Chickadee at the squirrel-proof feeder on my front deck.
I also have a heated birdbath, next to the feeder, it's been hard to keep it filled as the water evaporates so quickly in the cold and dry air.
I love watching the birds, and my cat, Amenti, loves watching the squirrels. Apparently the feeder and bath are not for the birds, but entertainment for the cat!
And finally, I thought I'd have a little fun (it's all relative).
I was going back through some old posts and found this picture (to the left) that I took of my yard on October 11th (original post here).
The growing season ended with a hard freeze on September 15th (average first frost occurs on that date), but some of the Sugar Maple's kept their leaves a few more weeks. The first snow didn't fall until November 7th, almost a month after this picture. And then there is this second picture (to the left), taken today, March 7th - almost five months after the first.
I would like to take another picture to add to this series after the snow melts and things begin to green up... but that's a month or two away.
Currently, at 13:27, it's 8.3 with a wind chill of 4 degrees and mostly sunny skies. Dew point is -14.9 making an RH of 33% and pressure is 30.49 "Hg.
Chilly last night, colder tonight?
The birds must be cold! 
And finally, I thought I'd have a little fun (it's all relative).