A heatwave baking the US Southwest for weeks is set to expand into central and eastern regions.
Beginning in the Midwest, meteorologists say the hot weather will extend east as far as the southern tip of Florida by Wednesday.
Temperature records were surpassed in several major cities over the weekend, and some 59 million Americans began today under extreme heat advisories.
July is expected to be the Earth's hottest month since records began.
On Sunday, the city of Phoenix, Arizona, extended its streak of temperatures above 43 degrees Celsius into a 24th day, well past the previous record of 18 days set in 1974.
At least 18 heat-related deaths have occurred in surrounding Maricopa County since April, with 69 more deaths under investigation.