Record-smashing US heat wave surges from West to East

A record-smashing heat wave was spreading Tuesday from the West toward the East Coast, placing nearly 100 million Americans under heat alerts.

The phenomenon known as a heat dome has already shattered all-time temperature records in western states, including 111F (44C) in Billings, Montana, where the previous record was 108F, and 109F in Salt Lake City, where the previous one was 107F.

Extreme heat and humidity persist in the west but are now expanding to the densely populated East Coast, which also faced brutal temperatures earlier in the month.

"Above average temperatures and dangerous levels of heat are forecast to enter the Northeast on Tuesday before the most intense heat occurs on Wednesday and expands into the Mid-Atlantic," said the National Weather Service.

Cities from Richmond, Virginia, to Boston, Massachusetts, are set to see temperatures soar from the upper 90s to near 100 degrees, with daily highs under threat.

Cooler temperatures are expected to follow by the end of the week.

Scientists from the World Weather Attribution group released an analysis showing the hot and humid conditions in the earlier East Coast hot spell -- which fell as America celebrated its 250th anniversary on July 4th -- would have been "virtually impossible" without human-caused climate change.

Heat domes can cause "dry thunderstorms," in which rain evaporates before hitting the ground and lightning strikes are liable to trigger wildfires, as much of the western United States is already experiencing drought conditions.

Scientists say a brewing "super" El Nino in the equatorial Pacific could also be influencing the heat dome.

Record-warm sea surface temperatures in the central Pacific are shifting where tropical storms form and release energy, which in turn is distorting the jet stream over the western US and allowing hot air to get trapped in place.

US forecasters expect El Nino to peak between October-December at potentially record-breaking levels, with the strongest spike in temperature to follow in 2027.

Compounded with human-induced climate change, the last El Nino contributed to making 2023 the second-hottest year on record and 2024 the all-time high.

ia/dw

© Agence France-Presse