A FREEZE WATCH has been issued for all of northern Illinois and southern Wisconsin beginning late Friday night, lasting through Saturday morning. A strong cold front will pass through the Stateline Thursday evening as light rain showers fall to the south. Shifting winds to the north will pull down a much cooler air mass Friday afternoon with highs only reaching the upper 40s and low 50s.
An even colder air mass will settle in Friday night with the arrival of high pressure to the west, bringing temperatures area wide down into the upper 20s and low 30s. Frost, and possibly a widespread, heavy frost, may occur if the center of the high falls close to northwest and north-central Illinois (which it looks like it may). Current forecast lows range from 27 degrees to 30 degrees across the area.
There are some plants that are a little more hardy than others, but it’ll be a good idea to either bring in or cover up any plants you’re able to. You can do that with either an old bed sheet, drop cloth, plastic or frost protection cover. You can even use an inverted planting pot or cut the bottom out of an old milk jug to put over the plant. Loosely cover the plants so that there is still some air flow around them. It’s best to cover either late afternoon or early evening, before the sun sets. You can even lightly water around the plant the day before so that soil has a little more moisture in it before the freeze occurs. A wet soil is able to retain more heat than a dry soil, keeping the surrounding air around the plant a little warmer. Make sure to remove the cover after sunrise Saturday as temperatures begin to warm.