Cities throughout the Midwest and eastern United States prepared on Sunday for yet another day of perilously high temperatures due to an unusual June heat wave affecting part of the region.

By 7:30 a.m. on Sunday, the temperature in the Chicago area had already climbed to 80 degrees Fahrenheit (26.6 degrees Celsius), as reported by the National Weather Service. Predictions indicated that the heat index would range 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. Meanwhile, in Columbus, Ohio, temperatures were already at 77 degrees Fahrenheit (25 degrees Celsius) by 8:30 a.m. The highs for the day were forecasted to reach 97 degrees F (36 degrees C), with the 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.