More than 70 million people in the US are under heat alerts. Go indoors and hydrate

PHOENIX — Over 75 million people in the United States were under extreme heat alerts Monday as a heat wave moved eastward, and the mid-Atlantic and New England were likely to see highs in the 90s as the week progresses. Excessive humidity will make it feel even more oppressive.

The U.S. last year saw the most heat waves, consisting of abnormally hot weather lasting more than two days, since 1936. Officials again warned residents to take precautions.

Much of the Midwest and Northeast were under heat warnings or watches.