CHICAGO (AP) — Public housing officials in Chicago were planning wellbeing checks on residents as the heat and humidity are expected to mount to dangerous levels as part of a wave of sweltering weather covering a substantial portion of the United States.

Excessive heat warnings were posted Thursday by the National Weather Service from central Nebraska and Missouri into western Ohio and parts of West Virginia. An excessive heat watch was put in place for the Cleveland area, part of New York State and parts of the East Coast.

Temperatures topping 100 degrees were expected for the southern and central High Plains.

Detroit was expected to reach 90 degrees Fahrenheit Thursday, according to the National Weather Service. A high of 91 degrees Fahrenheit was forecast for Chicago and the Baltimore and Washington D.C. areas. Cleveland was to see 92 degrees Fahrenheit, while a high of 96 degrees Fahrenheit was expected in Louisville, Kentucky, and St. Louis, Missouri.

Ambulances in Oklahoma’s two largest metropolitan areas of Oklahoma City and Tulsa have responded to more than 40 heat-related calls since Tuesday, most in the late afternoon as the temperature peaks.

“We’ve had people who have been walking,” said Emergency Medical Services Authority spokesman Adam Paluka in Tulsa. “We’ve had people who have been gardening. It doesn’t matter how much you’re doing or how little you’re doing, the heat can still affect you.”

At Cook County Health in Chicago, staff has been placed on-call and operational meetings are being held with emergency room leaders, said Dr. Trevor Lewis, interim chair of the health system’s Emergency Medicine department.

“We have a lot of festivals in the city over the weekend. We make appropriate plans for that,” said Lewis, adding that informing people how to take precautions during extreme heat is the best precaution.