Thread: Why is it so Hot Everywhere?

Heat wave menacing Southwest to break records in more cities before easing

"Dangerously hot" conditions may peak across portions of interior California, the Great Basin, the Southwest and South Texas on Friday. Still, extreme heat is likely to "plod" into next week, the National Weather Service warned.

The big picture: Heat alerts remain in effect for about 25 million people Friday, after widespread temperature records were tied or broken in California, Nevada and Arizona Thursday — including in Phoenix, where 11 people who were waiting in line to enter a Trump rally were hospitalized due to heat-related illnesses.

By the numbers: The temperature in Phoenix reached a record daily high of 113°F on Thursday, according to the NWS. The 85°F overnight minimum temperature was a record for the date, at 9°F above average.

• More records are likely to fall there Friday.
• Numerous temperature records were broken across Nevada on Thursday — including in Death Valley, which hit 122°F, and Las Vegas, which reached 111°F. Las Vegas tied the earliest date for a reading of 110°F or higher.
• New daily record highs set in California included 115°F in Needles and 111°F in Barstow, per the NWS.
• Several Texas cities have also had a record-setting week — including in San Angelo, which hit a daily high of 111°F on Tuesday and which was still experiencing triple-digit temperatures on Thursday.

Threat level: Extreme heat is responsible for more deaths than any other weather event, per the NWS.

• An AP analysis last week of CDC data found over 2,300 U.S. death certificates in 2023 noted excessive heat. As new temperature records are set, there are concerns 2024 could see even more heat-related deaths in the U.S.
• There will be "little to no overnight relief from the heat" for those "without effective cooling and/or adequate hydration," said the NWS in a forecast discussion on Thursday.

Context: A heat dome that's smashed records across Mexico and Central America repeatedly broken for weeks and which expanded north and west into the U.S. is behind the record temperatures.

What's next: The heat is expected to ease somewhat after Friday in the Southwest, but it may not completely dissipate.

• The heat dome associated with the heat began building across the Southwest on Tuesday and is forecast to peak in intensity Friday before "sliding off slowly toward the southern Plains during the next couple of days," per a NWS forecast discussion.
• It's also expected to expand slightly northward into Oregon and Washington.
• However, it may not be completely done influencing the weather across the Southwest in particular.

The intrigue: A NWS extended forecast discussion issued Friday morning found the heat dome will continue to cause "much warmer than average temperatures, but seemingly not quite as hot as in the short range period."

• The heat next week is forecast to be most intense across the Great Basin, and eventually into the Rockies and Plains states, the NWS stated.
• Some temperatures near at above 110°F may prove stubborn in the Southwest, however, the weather and climate agency noted.

Between the lines: Studies show climate change is causing heat waves to be more intense, longer-lasting and more frequent.

• Attribution studies of specific extreme heat events, such as the deadly 2023 heat wave in the U.S. and Europe, have detected climate change's fingerprints.
• One study last year found record heat in the U.S., Europe and Asia in July would have been "virtually impossible" without climate change.
• The severity of the long-duration heat wave across Mexico has been linked to human-caused climate change. Some seasonal computer model projections show this heat dome could migrate to a more permanent position across the Southwest later in the summer.