Seniors and other sensitive populations, beware: This weekend could be a hot one.
High temperatures in the 90s and high humidity Saturday and Sunday could make it feel like 100 to 110 degrees, according to the National Weather Service.
The heat wave is expected to start Friday, with high temperatures ranging from the high 80s to low 90s.
High temperatures Monday were predicted to be about 95 degrees, but there is a chance the day could be hotter than expected.
The weather service said the heat could linger into Tuesday, but residents should stay tuned for forecast updates.
An excessive heat watch for Cook County, Illinois, will be in effect from Saturday morning to Monday night. Chicago is a "heat island," and nighttime lows this weekend could fall only into the 80s.
In Northwest Indiana, nighttime lows in the mid-70s are expected Saturday and Sunday night.
The extended period of heat, nearly full sunshine and oppressive warmth at night could lead to hazardous conditions for seniors and those with pre-existing health conditions, forecasters said.
When excessive heat lingers for more than one day, human bodies don't have time to cool down, the weather service said.
Extreme heat can cause breathing problems, heat cramps, heat stroke or could lead to illness or death.
Residents should check on friends, family and neighbors; wear loose-fitting clothes; drink plenty of water; avoid strenuous activities in the heat; stay in the shade; and try to stay in an air-conditioned area.