Overview
- The National Weather Service says the heat dome will keep temperatures about 10°F above normal this week, driving air temperatures into the lower 90s in Chicago and the upper 80s across much of the region.
- Humidity will make conditions feel hotter than the air temperature with Chicago’s heat index forecast in the upper 90s and the south suburbs near 105°F during the peak period.
- Forecast models show the hottest conditions arriving Tuesday–Wednesday followed by a chance of storms Wednesday night into Thursday that will usher in a cooldown to seasonable highs in the low 80s by Thursday–Friday.
- Heat index values near or above 105°F substantially raise the likelihood of heat illness by making it harder for the body to cool itself, which is why public-health officials point to the July spike in Cook County heat deaths as a warning.
- Long-range guidance projects several more weeks of above-normal warmth with daily highs mostly in the upper 70s to 80s, meaning elevated heat and humidity could persist even after this week’s brief cooldown.