Cities throughout the Midwest and eastern United States prepared on Sunday for more hazardous heat as an unusual June heat wave maintained its hold over parts of the nation.

By 7:30 a.m. on Sunday, temperatures in the Chicago area had already climbed to 80 degrees Fahrenheit (26.6 degrees Celsius), as per the National Weather Service. Forecasts predicted heat indices ranging from 100 to 105 degrees F (37.7 to 40.5 degrees C).

In Pittsburgh, the heat index was anticipated to exceed 105 degrees F. Columbus, Ohio, recorded 77 degrees Fahrenheit (25 degrees Celsius) by 8:30 a.m. Local temperatures were predicted to peak at 97 degrees F (36 degrees C), with a heat index nearing 104 degrees F (40 degrees C).

Sunday marked the second straight day of extreme heat across the Midwest and East Coast. Heat indices on Saturday hit 103 degrees F (39.4 degrees C) in Chicago and 101 degrees F (38.3 degrees C) in Madison, Wisconsin, turning that city’s annual naked bike ride into a sticky and sweaty affair. Minneapolis baked under a heat index of 106 degrees F (41.1 degrees C).

The heat is expected to persist into the coming week, with the hottest temperatures shifting eastward. New York City is expected to see highs around 95 degrees F (35 degrees C) on Monday and Tuesday. Boston is on track for highs approaching 100 degrees Fahrenheit (37.7 degrees Celsius) on Tuesday, and temperatures in Washington, D.C., were expected to hit 100 degrees F on Tuesday and Wednesday.