The season's first frost is expected tonight as overnight lows drop into the low to mid 30's. The National Weather Service has issued a Frost Advisory for Green, Rock, Walworth, Jo Daviess, Stephenson, Winnebago, Boone, Ogle, and Carroll counties from 2am - 9am Thursday morning. Clear skies, cold air, and lighter winds will allow temperatures to fall and frost to develop. You'll want to cover any sensitive plants before you head to bed.
That cold front is currently in far northwestern Illinois and is sinking to the southeast. This is already switching our winds from the south to the north and ushering in colder air.
Temperatures will reach their highs around 10am and then will fall through the 50's throughout the afternoon.
Highs Thursday will only make it into the mid 50's despite abundant sunshine, as an arctic high is settled overhead. We could actually see frost develop again Thursday night into Friday morning as temperatures fall into the mid 30's once again. However, the cold air won't be as strong, so the frost will be contained to more outlying and low lying areas Friday morning.
Good news is, the weekend kicks off a string of 70's!