Update: Frost Advisory Chicago area early this Sunday morning and again early Monday morning
The Chicago National Weather Service Forecast Office has issued a Frost Advisory (blue-shaded area in the highlighted map) in effect from Midnight CDT until 8AM CDT this Sunday morning and again Monday morning for the Chicago area. Note the Advisory extends into adjacent areas of Wisconsin, Indiana and western Illinois.
Cool dry Canadian-source high pressure will be over our area overnight with mostly clear skies and light winds allowing temperatures especially in low-lying frost-prone areas such as the Rock and Fox River Valleys to possibly drop into the low and middle 30s. Sensitive plants should be protected as much as possible.