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CHICAGO — The expected dangerously hot weather in and around Chicago has officials warning people to drink lots of water, avoid going outside for long stretches and find a cool spot to ride out the heat.

An Excessive Heat Warning (purple-shaded area on the headlined map) is in effect for the entire Chicago area, including Chicago as well as northern Illinois into northwest Indiana, starting later this Friday morning and continuing through Saturday into Saturday night.

Very dangerous heat indices should range from 105 to 115-degrees with even higher values possible as temperatures reach into the middle and upper 90s during the afternoon and overnight low temperatures fail to provide much if any relief dropping only into the upper 70s and lower 80s – highest overnight readings in the city of Chicago.

With only thin clouds at times, the afternoon sun will effectively add another 5 to 15-degrees to the heat indices, making conditions even more dangerous.

Recent rains, evapotranspiration from a growing corn crop and high dew-point air flowing into our area from the Plains and Mississippi Valley will all contribute to very high humidity values, resulting in near-record high overnight temperatures, providing no relief from the heat at night, especially in the Chicago “heat island”.

Tips for staying safe and staying cool

County officials offer these tips to stay safe during the heat.

  • Drink plenty of fluids
  • Never leave a child or pet in a hot car
  • Avoid drinks with caffeine or alcohol
  • Try to stay in the shade or indoors as much as possible
  • Check on elderly neighbors and those with functional needs
  • Take pets indoors and make sure they have plenty of water

Make sure you check-on and assist those most susceptible to the heat and humidity: people with respiratory or heart problems, children and elderly, especially those with no access to air-conditioning.

If you must be outside during the late-morning/afternoon, stay out of the sun as much as possible, seek shade and drink plenty of water.

Hot and humid conditions through the weekend will give way to slightly cooler temperatures and lower humidity on Monday, but more heat and humidity return after that. With exception of Monday within several miles of Lake Michigan, the seven-day forecast calls for Chicago’s afternoon temperatures to be in the 90s on every day.