Holiday heat wave: As temperature climbs across much of U.S., so does the danger

Forecasters warn of scorching conditions in the Midwest and Great Lakes states. The Northeast is up next.

DETROIT — Nature’s oven was on high Tuesday for millions of people in the Midwest and Great Lakes states as intense heat and humidity baked the regions with no immediate relief before the misery shifts to the eastern U.S.

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The National Weather Service was blunt: Conditions were “dangerous” as the heat index, a combination of air temperature and humidity, exceeded 100 degrees Fahrenheit in some areas. It warned about a risk for heat-related illnesses, especially among people without air conditioning.

Detroit’s air temperature was in the high 90s, the Weather Service said, and could even reach 100 at some point through Thursday. The city said a dozen recreation centers were open, some until 11 p.m., for people to cool off. Big chunks of Michigan, as well as Illinois, Ohio, Indiana, Kentucky and much of Iowa, were under an extreme heat warning.