Coldest air thus far

At 4:33 AM this morning looking at the SFC OBS for Northern MN and Northern WI...I see temps in the middle 30s to lower 40s...I'm sure they will drop a few more degrees before sunrise...Here on my weather station I have a temp of 39.9 °..Thus making this the coldest air so far this later summer really early fall.....Looks like temps will rebound nice today right into the middle to upper 70s.....