Phoenix, Arizona, hits its 100th consecutive day of 100F weather

Phoenix, Arizona , saw its 100th straight day of 100F (37.7C) heat this week.

The hottest large city in the United States broke its previous record of 76 consecutive 100F days set in 1993. The relentless streak, which started on 27 May and hit its 100th day on Tuesday, is forecast to persist into next week. An excessive heat warning is in effect through Friday, with temperatures expected to reach 110F (43C) tomorrow.

This summer was the hottest one in Phoenix since 1896, when records first began. Latest county data shows that at least 177 people died from heat-related causes so far this year, with 436 under investigation. Last year, Maricopa county saw 645 confirmed heat-related fatalities, enduring 55 days in a row with above 110F temperatures.

Related: ‘Dangerously hot’ weather roasts US west as brutal summer continues

“Summers in Phoenix are becoming increasingly hotter, with more intense and prolonged heat,” said Shel Winkley, a meteorologist at the non-profit Climate Central. “On average, Phoenix now experiences about 60 days [or] 65% of the summer with extreme heat.”

In addition to Arizona, millions of Americans across Nevada and California are facing scorching heat, with the highest temperature expected to peak in the Death Valley national park at 120F (49C).

“Temperatures will be running up to 8 degrees above normal for early September,” the National Weather Service Las Vegas office warned in an advisory.

Homeless people, children, the elderly, pregnant people and those with chronic medical conditions are at higher risk for heat-related illness .

Related: Heat-related deaths in Phoenix, Arizona, have nearly doubled this year

“Consecutive high heat days mean that people in Phoenix don’t get respite at night, especially those who don’t have or can’t afford to run an AC unit as well as those who work outdoors,” said Juan Declet-Barreto, senior social scientist for climate vulnerability at the Union of Concerned Scientists.

“I would like the public to understand that this heat is no longer a rare occurrence,” Declet-Barreto said. “It will continue to get worse year after year if we don’t make drastic emissions reductions. We need to decarbonize our energy, industrial, agricultural and transportation sectors. There’s no way around that if we want cities like Phoenix to be livable.”