BOSTON — Dangerously high temperatures are expected to spread across the Central and Eastern United States on Wednesday through the weekend, with temperatures soaring above 100 degrees Fahrenheit in the hardest-hit places, the National Weather Service has warned.

And even when the sun dips below the horizon, temperatures in many places are expected to remain in the 80s.

The hottest part of the country? Smack dab in the middle.

Everyone living in the region stretching from northern Oklahoma and central Nebraska through Iowa, Missouri and western Illinois should brace for a “prolonged period of dangerously hot temperatures and high humidity,” the warnings say. People in central and south central Kansas should expect to endure highs of about 102 degrees; the temperature in Des Moines was expected to hover around 100.

Excessive heat warnings have also been posted farther east, for parts of New Jersey, Delaware and Pennsylvania.