The agency warned that extreme heat poses a danger in the evening as well, as temperatures are expected to remain above average overnight. As of Monday morning, nearly 8 million Americans were under heat alerts, according to the National Integrated Heat Health Information System.

Parts of California, Oregon and Washington state will experience extreme heat at least through Tuesday, forecasters say.

More than 30 million Americans are on alert for scorching heat with triple-digit temperatures breaking records. Plus, evacuations grew in California’s wine country as a large wildfire grew overnight.