It’s hot. And it’s going to stay hot for millions of Americans. These graphics explain the trend

It’s been a scorching summer for many Americans, with tens of millions living in areas under extreme heat.

Over the last three weeks, more than a third of the population has experienced weekly average maximum temperatures above 90 degrees, particularly in the southern half of the country.

Last week, nearly 12% of Americans dealt with average highs topping 100 degrees, according to the US Centers for Disease Control and Prevention. That’s the highest percentage of Americans feeling average highs in the triple digits so far this summer.

The agency’s Heat and Health tracker examines where Americans are experiencing extreme heat conditions so communities can prepare for — and respond to — such events.

While the South and West have experienced the highest temperatures over the last two months, by the end of July, temperatures exceeding 90 degrees had spread across the South, Midwest — and even the north central United States, including the Dakotas and Montana.

During the last week of July, nearly 155 million Americans saw weekly average high temperatures above 90 degrees, 28 million of whom saw average highs topping 100 degrees.

In the first week of August, the number of people feeling three-digit temperatures jumped to 38 million, mostly in Texas, Oklahoma and southern Arizona, including Phoenix.

More than 53 million Americans across 473 counties are expected to experience dangerous levels of heat for at least five days in August, data from the CDC and the US Census Bureau show.

Sixty-four of those counties, scattered throughout the South and West, may see dangerous temperatures for 10 days or more.