The extreme heat scorching the US city of Phoenix, Arizona, has set a new record, the 19th consecutive day temperatures hit at least 110F (43C) in a summer of suffering echoing around much of the globe.
As human-caused climate change and a newly formed El Nino are combining to shatter heat records worldwide, the Phoenix region stands apart among major metropolitan areas in the US.
No other major city – defined as the 25 most populous in the United States – has had any streak of 110-degree days or 90-degree nights longer than Phoenix, said weather historian Christopher Burt, of the Weather Company.
National Oceanic and Atmospheric Administration (NOAA) climate data scientists Russ Vose and Ken Kunkel found no large cities with that streak of warming, but smaller places such as Death Valley and Needles, California, and Casa Grande, Arizona, have had longer streaks.
Death Valley has had an 84-day streak of 110-degree temperatures and a 47-day streak of night-time temperatures that have not fallen below 90, Mr Vose said.
For Phoenix, it is not only the brutal daytime highs that are deadly.
The lack of a night-time cooldown can rob people without access to air conditioning of the break from the heat that their bodies need to continue to function properly.
With Tuesday’s low of 94F, the city has had nine straight days of temperatures that did not go below 90F at night, breaking another record there, according to National Weather Service meteorologist Matt Salerno, who called it “pretty miserable when you don’t have any recovery overnight”.
On Monday, the city set a record for the hottest overnight low temperature: 95F (35C).
Some 200 cooling and hydration centres have been set up across the metro area to cool residents, but both shut down between 4pm and 7pm due to staffing and funding issues.
“Long-term exposure to heat is more difficult to withstand than single hot days, especially if it is not cooling off at night enough to sleep well,” said Katharine Jacobs, director of the Centre for Climate Adaptation Science and Solutions at the University of Arizona.
The last time Phoenix did not reach 110F (43.3C) was on June 29, when it hit 108F (42.2C).
The record of 18 days above 110F that was tied on Monday was first set in 1974, and it appeared destined to be shattered with temperatures forecast above that through the end of the week.
“This will likely be one of the most notable periods in our health record in terms of deaths and illness,” said David Hondula, chief heat officer for the City of Phoenix.
“Our goal is for that not to be the case.”
Phoenix’s heatwave has both long and short-term causes, said Arizona State University’s Randy Cerveny, who co-ordinates weather record verification for the World Meteorological Organisation.
“The long-term is the continuation of increasing temperatures in recent decades due to human influence on climate, while the short-term cause is the persistence over the last few weeks of a very strong upper level ridge of high pressure over the western United States,” he said.
That high pressure, also known as a heat dome, has been around the Southwest cooking it for weeks, and when it moved, it moved to be even more centred on Phoenix than ever, said National Weather Service meteorologist Isaac Smith.
The Southwest high pressure not only brings the heat, it prevents cooling rain and clouds from bringing relief, Mr Smith said.
Normally, the Southwest’s monsoon season kicks in around June 15 with rain and clouds.
But Phoenix has not had measurable rain since mid-March.
“Although it is always hot in the summer in Phoenix, this heatwave is intense and unrelenting,” said Ms Jacobs.
“Unfortunately, it is a harbinger of things to come given that the most reliable projected impacts of climate change are those that are directly related to the increase in global temperatures.”
