Colder air plunged into southern Wisconsin on Saturday, behind a cold front and vigorous low pressure system which brought early morning thunderstorms to the area. Many locations experienced small hail in the thunderstorms. The rain even became mixed with or changed to light snow for a brief period in the Green Lake, Fond du Lac and Beaver Dam areas Saturday morning.
High pressure passed slowly across the region from Saturday night through Sunday night. Mainly clear skies and light winds at night allowed temperatures to tumble into the upper 20s to middle 30s over south central Wisconsin, and southeast Wisconsin away from Lake Michigan both Saturday night and Sunday night.
Some of the coldest temperatures reported this (Monday) morning around southern Wisconsin include 27 at Lone Rock, Mazomanie, Arlington and Darlington, 28 at Lodi and Baraboo, 30 at Reedsburg, Beaver Dam, Slinger, Hartford, Hales Corners and Burlington, 31 at Black Earth, Watertown, Beloit and Union Grove, 32 at Brodhead, Waukesha and Kenosha.
Here are a pair of graphics depicting the low temperatures Monday morning from around southern Wisconsin and the entire state:
Here is a graphic depicting the low temperatures Sunday morning from across the entire state:
As you can see from the below graphic, we are well ahead of schedule this year in dealing with freezing temperatures across southern Wisconsin.
Breezy southwest winds will pull warmer air into southern Wisconsin today. Afternoon temperatures will peak 10 to 15 degrees warmer than the same time yesterday. The mild temperatures will stick around on Tuesday before slightly cooler air filters back in for the rest of the work week. A front will pass through southern Wisconsin rather uneventfully on Tuesday resulting in the slightly cooler temperatures. However temperatures will remain seasonal for late September through the end of the week.
National Weather Service Milwaukee/Sullivan, WI