Extreme heat alerts are in effect for tens of millions of people in the United States as cities including Chicago break heat records. States in the Midwest started to bake Monday in a dangerous heat wave that was expected to stretch from Iowa to Maine into at least Friday. The mid-Atlantic and New England are 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 since 1936. Officials are warning people to take precautions such as drinking plenty of water and staying indoors.
