Chicago weather: Dangerously hot weather returns this week

Emily Wahls has your weather update!

Chicago weather forecast

What to Expect :

CHICAGO - Temperatures tonight will bottom out in the upper 60s and low 70s before humidity starts to ramp up enough for areas of patchy fog Tuesday morning. After sunrise, skies will become partly cloudy with highs in the upper 80s. Humidity is expected to steadily increase late Tuesday into Wednesday.

The potential for record warmth exists on Wednesday with forecast high temperatures in the upper 90s. The record high temperature for July 23 is 97° F set in 2012. Thursday looks to be a carbon copy of Wednesday; except for the morning, the low temperature will remain in the upper 70s and potentially the low 80s if enough cloud cover remains overhead Wednesday night. Winds will be out of the southwest, which means the extreme heat will be felt all the way to the lake shore.

Early Friday morning, a "cold front" will advance through northern Cook County and lead to scattered showers and thunderstorms before sunrise. Throughout the day Friday, scattered showers and thunderstorms may pop up as the front stalls near I-80; however, high temps will still climb into the upper 80s Friday afternoon.

Saturday highs are expected to be in the upper 80s and another round of brief scattered showers and thunderstorms remains a possibility for the afternoon. Sunday turns the heat back up to the low 90s and some brief showers and thunderstorms may impact the area late in the afternoon.

What are Heat Index Values?

The Heat Index is essentially the "feels like" temperature for the summer season. It takes into account humidity and how it can impact the way the temperature feels to the human body. In high humidity and scorching hot temperatures, perspiration will not evaporate as quickly, which may lead to heat-related illnesses. When humidity is low, perspiration evaporates more quickly, allowing our bodies to cool down more efficiently.