History-making heat set to spread after weekend of triple-digit temperatures

A history-making heat wave that baked Southern U.S. communities with triple-digit temperatures over the weekend will offer little relief this week and could spread dangerous conditions farther across the Sun Belt.

About a third of U.S. residents were under excessive heat advisories or warnings Sunday as firefighters fought fast-moving brush fires in Southern California, temperatures neared 130 degrees Fahrenheit in Death Valley, California, and some areas — including El Paso, Texas — marked a month of 100-plus temperatures.

The center of the heat wave is expected to spread eastward Monday, with extreme temperatures continuing through at least next weekend, according to the National Weather Service. Heat indexes this week are expected to spike to dangerous levels along the more humid Gulf Coast and in the Southeast. Heat warnings were in the forecast for communities in the Pacific Northwest to the tip of Florida.

Meanwhile, Northeastern states this weekend were hammered with heavy storms and excessive rain over the weekend, which had canceled more than 1,320 flights as of Sunday afternoon and killed at least four people. Smoke from wildfires in Canada also moved through the Great Plains and the Midwest over the weekend, prompting air quality alerts from Montana to Ohio.

The dramatic weekend of intense heat, storms and smoke punctuated a summer of extremes that highlights how climate change is shifting risk across the country and making it more likely that dangerous, anomalous weather will sting multiple regions at once.

Arizona's Extended Extreme Heat Wave On Track to Break Its Record For Longest Stretch Of Days Over 110 Degrees (Brandon Bell / Getty Images)
Arizona's Extended Extreme Heat Wave On Track to Break Its Record For Longest Stretch Of Days Over 110 Degrees (Brandon Bell / Getty Images)

Heat kills more people every year than other weather hazards. Heat waves can be more threatening the longer they linger, because stress accumulates over time when people can’t find adequate respite.

This week could be particularly dangerous for communities like Phoenix, which could experience its hottest-ever seven-day stretch, according to the National Weather Service. The city, along with its surrounding suburbs in Maricopa County, Arizona, recorded 425 deaths associated with heat last year.

Sunday marked the 17th day in a row that Phoenix high temperatures hit or exceeded 110.

“We’re currently on pace to break the all-time consecutive streak of 110-degree days. Currently that record is 18 days,” said Gabriel Lojero, a National Weather Service meteorologist in Phoenix. “We’re forecasting temperatures to be near or above 115 this week, so it’s likely we’re going to break that record.”

Lojero said he worried about people who are unsheltered or don’t have easy access to air conditioning.

“There’s no relief. It’s a cumulative issue,” he said. “Your body is not able to recuperate.”

Lojero said nothing in the forecast suggested Phoenix would get a break from the heat any time soon. High temperatures were expected to continue through next weekend, and there were no signs of thunderstorms, which are typical of the summer monsoon season in the desert Southwest.

“In the monsoon season, usually we get thunderstorm activity. You get more cloud cover and rain. That helps mitigate those extreme temperatures,” Lojero said. “Unfortunately, at least through this upcoming week, we are not seeing that.”

This article was originally published on NBCNews.com