Dangerous US heat wave pushes eastward, capping globe's record July

An intensifying heatwave descended on the eastern US on Thursday, prompting warnings about the dangers presented by the sweltering heat and humidity in the final days of a record-smashing July around the world.

Some 180 million Americans - about half the population of the US - are under heat watches and warnings, with temperatures and heat index values well above 37.8 Celsius in the forecast until at least Saturday, the National Weather Service said.

Officials in New York City, Washington DC, Philadelphia and other big cities urged people to avoid working or playing outside, to drink plenty of fluids and to check on loved ones and neighbors.

"The next four days will be extremely hot - take care of yourself and the people around you," Washington Mayor Muriel Bowser said on X social media platform, formerly known as Twitter. The nation's capital was expected to see the heat index, a measure of what the temperature feels like to the human body, reach 41.7 C.

In Philadelphia, officials declared a health heat emergency until Saturday and created a phone help line for the elderly, opened cooling centers and increased homeless outreach.

Cooling centers have also been opened across New York City for those who do not have access to air conditioning. The heat index could reach 39.4 C on Friday in the most populous US city.

"Heat is deadly, and climate change is making extreme heat more frequent and even more dangerous, especially for vulnerable New Yorkers," New York City Health Commissioner Ashwin Vasan said in a statement.

The growing frequency and intensity of severe weather is symptomatic of global, human-driven climate change that is fueling extremes, experts in the field say, with current heat waves expected to persist through August.

June 2023 was the hottest on record in the US, dating back to 1850. It also was the 47th consecutive June and the 532nd consecutive month with temperatures above the 20th-century average, according to the weather service.

This month is also shaping up to be a record-breaker on a global basis. Thousands of tourists fled wildfires amid baking temperatures in Greece, while temperatures in a northwest China township soared as high as 52.2C.

An analysis by Germany's Leipzig University released on Thursday found that July 2023 will shatter heat records, with this month's mean global temperature projected to be roughly 1.5 degrees Celsius above the pre-industrial mean.

This would make this July at least 0.2C warmer than the same month of 2019, the former hottest in the 174-year observational record, according to European Union data.

A prolonged heatwave has been parked over the US Southwest for weeks. Phoenix, Arizona, is expected to see its 28th consecutive day of temperatures above 43.3 C on Thursday, shattering the previous record of 18 straight days.