CHICAGO — A Frost Advisory is in effect for most of the northern half of the Chicago area early Sunday morning.
Near-record low temperatures early Sunday morning will lead to possible widespread patchy frost across at least the portion of the Chicago area north of Interstate-80 early Sunday morning (note blue-shaded area on headlined map above). While not included in the Frost Advisory, patchy frost could also occur in frost-prone locations in Chicago/Cook County and the remainder of the Chicago area south of Interstate-80. Take precautions to protect temperature-sensitive plants tonight.
With clearing skies and exceptionally cold high pressure for this time of the year moving into the Northern Plains, Midwest and western Great Lakes, there is a strong possibility of at least scattered frost across northeast Illinois into northwest Indiana – the more likely area to be hit is north of Interstate-80 to the north and west of Chicago. To understand the unusually cold nature of the air mass moving into our area, Chicago’s record low temperature for May 15 is 35-degrees – set over 120 years ago in 1895. Measured officially at 5 to 6-feet above the ground, in frost-prone areas, temperatures could easily fall into the lower 30s at ground-level.
The widespread impact of the unseasonably cold air mass is depicted on the map below showing the widespread Freeze (purple-shaded areas on the map above calling fro temperatures in the mid to upper 20s) and Frost Advisories (blue-shaded areas) to our west and north.
And a warning for gardeners: you might want to cover up plants, or if possible, bring them inside overnight.