An extreme heat warning for Cook County has been extended until early Friday as temperatures are expected to remain in the 90s all week, city officials and forecasters said. The warning, issued by the National Weather Service, began at noon Monday and now runs until 12 a.m. Friday, according to the city's Office of Emergency Management and Communications.The weather service had previously issued the extreme heat warning to remain in effect through Wednesday evening.As of 11 a.m. Tuesday, it was sunny, hot and 88 degrees at Midway Airport on the Southwest Side, and by 2 p.m. had surged to 93 degrees — one degree cooler than readings at O'Hare Airport — according to the weather service. Heat index values could get as high as 105, and southwest winds are gusting around 15 mph, and could reach 30 mph. Here is a look at the heat index forecast for select locations through Thursday. pic.twitter.com/wJaIkun05x— NWS Chicago (@NWSChicago) June 30, 2026 The record high temperature for June 30 was 99 degrees, set in 1953, according to the weather service.Tuesday night was expected to be mostly clear, with a low around 79, the weather service said.A high of 97 degrees is expected for Wednesday, 96 for Thursday and 92 for Friday, the weather service said.Heat-related illnesses can rise quickly during extreme heat events, OEMC said. Officials urged residents to stay hydrated, stay in air-conditioned areas, avoid the sun and check in on their relatives and neighbors.The anticipated heat and persistent warmth at night can lead to hazardous conditions, particularly for older adults and people with preexisting health conditions, OEMC said. Children look on as a Department of Water Management worker closes an open fire hydrant near South Christiana Avenue and West 28th Street in Little Village as temperatures spike in the Chicago area Tuesday. | Ashlee Rezin/Sun-Times 1 of 8 A pedestrian walks by a television screen that shows a heat index of 94 degrees in Aurora, Illinois during an extended warm weather alert in the Loop on Tuesday. | Pat Nabong/Sun-Times 2 of 8 A pedestrian shades herself from the sun with an umbrella during an extended warm weather alert in the Loop on Tuesday. | Pat Nabong/Pat Nabong/Sun-Times 3 of 8 A vendor refills ice in a cooler on West 26th Street in Little Village as temperatures spike in the Chicago area Tuesday. | Ashlee Rezin/Sun-Times 4 of 8 A person fans herself with a towel at Daley Plaza during an extended warm weather alert in the Loop on Tuesday. | Pat Nabong/Pat Nabong/Sun-Times 5 of 8 A pedestrian attempts to stay cool while walking on West 26th Street in Little Village as temperatures spike in the Chicago area Tuesday. | Ashlee Rezin/Sun-Times 6 of 8 A pedestrian wears sunglasses and holds a Gatorade during an extended warm weather alert in the Loop, Tuesday, June 30, 2026. | Pat Nabong/Sun-Times | Pat Nabong/Pat Nabong/Sun-Times 7 of 8 A pedestrian attempts to stay cool while walking on West 26th Street in Little Village as temperatures spike in the Chicago area Tuesday. | Ashlee Rezin/Sun-Times 8 of 8 ComEd said power outages remained low Tuesday morning. As of 9:30 a.m., about 875 customers were without power, and about 2,800 customers had their power restored earlier in the morning, according to Anthony Garcia, a ComEd spokesperson. The company's website showed more than 1,400 without power as of 6 p.m. Tuesday.Most of the outages as of Tuesday morning were in ComEd’s Chicago region, including Maywood. ComEd said it could not provide a more specific breakdown.Garcia said the current outage numbers were on the low end and that anything surpassing 100,000 customers without power would be considered a large outage.The extreme heat was a likely factor in some outages because transformers can overheat as customers use more power to stay cool, Garcia said. Related The heat inside your car can turn deadly in minutes this summer ...read more read less