Weather Alerts For Cortland, IL

# HEADLINE -------------------- HEAT ADVISORY IN EFFECT UNTIL 10 PM CDT THIS EVENING # DETAILS -------------------- WHAT Peak heat index values this afternoon of 100 to locally 110 degrees. WHERE Portions of north central and northeast Illinois and northwest Indiana. WHEN Until 10 PM CDT this evening. IMPACTS Hot temperatures and high humidity may cause heat illnesses. ISSUED AT Friday, September 4, 2026 at 2:54 AM CDT ISSUED BY National Weather Service Chicago IL HEADER URGENT - WEATHER MESSAGE # PRECAUTIONARY/PREPAREDNESS ACTIONS -------------------- Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. # AREAS AFFECTED -------------------- Kendall, Southern Will, Boone, Central Cook, De Kalb, DuPage, Eastern Will, Kane, Lake IL, Lake IN, Lee, McHenry, Northern Cook, Northern Will, Ogle, Porter, Southern Cook, Winnebago Including the cities of Oak Lawn, Sycamore, Channahon, Mundelein, Elgin, McHenry, Joliet, Yorkville, Lemont, Oak Park, Downers Grove, Chicago, Schaumburg, Portage, Algonquin, Park Forest, Dixon, Merrillville, Mokena, Palatine, Gary, Plano, Oak Forest, Hammond, Oregon, Valparaiso, Calumet City, Evanston, Oswego, Rockford, Byron, Orland Park, Gurnee, Bolingbrook, Beecher, Buffalo Grove, Des Plaines, La Grange, Wilmington, DeKalb, Manhattan, Rochelle, Plainfield, Lombard, Crystal Lake, Belvidere, Cicero, Waukegan, Peotone, Carol Stream, Chesterton, Crete, Naperville, Woodstock, Wheaton, Northbrook, and Aurora

Pollen Index: 10.2 Pollen Level: high Predominant Pollen: Ragweed, Chenopods and Grass. Pollen concentrations for Friday will be greater than today's levels and extend further into the very high range. This higher level is caused in part by higher temperatures and the lower dewpoint.