A Frost Advisory will be in effect from midnight tonight until 8AM Saturday morning across northeast Illinois into northwest Indiana (blue-shaded area on the headlined map). The best chance of frost will be when readings bottom-out in the low to mid 30s an hour or two before and after sunrise Saturday morning. Take time to protect temperature-sensitive plants.
A cloud cover over our area will gradually begin to move off to the east and thin-out later this evening and overnight, as the leading edge of cold dry Canadian-source high pressure noses into our area. After midnight temperatures should fall into the 30s with dew points in the 20s and diminishing northerly winds leading to an increasing chance of frost forming as sunrise approaches. Frost will be least likely along the immediate Lake Michigan shoreline and in the heart of Chicago.