Extreme heat warnings in effect in 28 states across US

<span>Photograph: Ross D Franklin/AP</span>
Photograph: Ross D Franklin/AP

The National Weather Service has warned that extreme heat will affect more than 100 million people in the US this week, with triple-digit temperatures in some states and broken temperature records in many areas across the country.

“Above-normal temperatures will continue to prevail across much of the US through the end of the week, with a significant portion of the population remaining under heat-related advisories and warnings,” the agency said.

Heat warnings and advisories have been put in place for 28 states, with central and southern states facing the brunt of the scorching heat.

Some parts of Oklahoma reached 115F (46C) this week, while the Dallas area hit 109F (42C).

Emergency medical services in Tulsa, Oklahoma, have reported an increase in heat-related emergency calls this year. The city’s Emergency Medical Services Authority said it has received nearly 250 calls this year, a number typically reached later in the summer.

“It’s very concerning,” the department’s Adam Paluka told CNN. “Especially because the amount of patients that are being transported indicates that some of those calls are heatstrokes, which can be deadly.”

In the north-east, where temperatures are settling in at more than 90F (32C), city leaders have warned residents to limit outside activity during the hottest times of the day.

Philadelphia declared a “heat health emergency” for Thursday and has set up a “heatline” number for residents experiencing intense heat. Boston has opened community centers and pools as places for residents to cool down.

“It is clear that a changing climate is a risk to our health,” Boston mayor Michelle Wu said Wednesday. “I urge everyone to stay cool and safe, and check on your neighbors this week.”

In Phoenix, America’s hottest city, an extreme heat warning was in place for Thursday and Friday. The temperature is forecast to hit 113F (45c) on Thursday afternoon and 115F (46C) on Friday afternoon. Heat advisories are only issued when temperatures are higher than average for the time of year, and in Phoenix in July that means temperatures over 112F. So far this year, the city has broken or equaled four daytime high records and nine nighttime lows.

The impact of heat is cumulative and the body only begins to recover when temperatures drop below 80F. Climate scientists have warned that heatwaves – which have spread throughout Europe and Asia this summer – will be more intense and prolonged if the climate emergency is not addressed. A study published in May showed that human influence on the climate made a particular heatwave in south Asia 30 times more likely to have happened.

Speaking in Somerset, Massachusetts, about the climate crisis on Wednesday, Joe Biden said that global heating is an “emergency” but failed to declare a national emergency, as activists hoped the president would. Such a declaration would allow Biden to block crude oil imports or to direct the military to work on renewable energy production. The White House said that a formal emergency declaration is “still on the table”.

“It is literally, not figuratively, a clear and present danger,” Biden said. “The health of our citizens and communities are literally at stake.”

Additional reporting by Nina Lakhani