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Where there will be extreme heat after the record temperatures this week
Where there will be extreme heat after the record temperatures this week

More than 135 million people in the 48 states of southern North America, including on both coasts and in some of the country’s largest cities, are under heat warnings on Wednesday. In many cases, the warnings have been in effect for days and will continue through the weekend. They come after a rough start to July that saw hundreds of heat records set.

In the west, Phoenix, Las Vegas, San Jose, Spokane, Washington, and Boise, Idaho, are under extreme heat warnings. In the east, heat warnings stretch from South Carolina to Massachusetts and include Washington, Baltimore, Philadelphia, and Boston. Heat indices – which take into account both air temperature and humidity – should reach 105 to 110 along much of the Interstate 95 corridor.

Much of the Lower 48 states are forecast to have a heat risk ranging from “significant” to “extreme,” or at least Level 3 on the federal government’s 0-to-4 scale.

The most persistent and widespread heat risk of Level 4, considered “extreme,” is concentrated in the desert southwest. On Sunday, Las Vegas recorded the highest temperature on record at 49 degrees.

Further extreme heat is forecast – especially in the west

Extreme heat will continue to ravage the Western United States for the remainder of the work week, with record-breaking heat waves forecast for parts of Washington state, Oregon, Idaho, California, Nevada and Arizona on Wednesday.

Las Vegas is expected to reach 119 degrees on Wednesday and Thursday. Were it not for Sunday’s high of 120, those would be all-time highs. If Sin City’s high reaches at least 115 degrees on Wednesday, it would be the fifth day in a row that’s that hot.

In the zone from Las Vegas to parts of Southern California and Arizona, highs of over 49 degrees are expected through Friday.

Temperatures will also continue to reach triple digits in regions as far north as western Canada, including much of eastern Washington state, the Snake River Valley in Idaho and much of the Great Basin.

For the rest of the work week, highs of at least 110 degrees Fahrenheit are forecast across much of California’s Central Valley.

It is expected to remain hot through the weekend, but likely to be below record temperatures in most areas as moisture from the south increases due to the onset of the monsoon season in the southwest.

However, forecasts suggest that the heat dome – a zone of intense high pressure responsible for the extremely high temperatures – will largely remain in place.

A cold front will cause the heat to ease somewhat in the eastern United States on Thursday and Friday, but the heat will pick up again over the weekend and into next week.

The heat has broken hundreds of records

Since early July, hundreds of heat records have been set across the United States, many of them in the West. Through July 9, the number of record highs exceeded the number of lows by nearly 20 times, according to data from the Southeast Regional Climate Center. On July 5, 6 and 7, about 300 heat records were set daily.

Many places in the West recorded at least four calendar day record highs in the first nine days of the month. These include Reno, Nevada; Las Vegas; Bishop and Redding in California; and Portland and Medford in Oregon.

At least somewhere in the West, new highs were being reached almost daily. On Tuesday, the high of 118 in Barstow, California – about halfway between Los Angeles and Las Vegas – set a new high for the third day in a row.

Several other locations have recorded all-time highs, including Palm Springs, California (124 on Friday), Redding (119 on Saturday) and Las Vegas.

On Sunday, Death Valley reached 59 degrees Celsius – one of the highest temperatures on record – and the average high temperature over the past seven days was 42.8 degrees Celsius.

In the east, Raleigh, North Carolina, reached 41.9 degrees Celsius on Friday – also a historic high.

Particularly notable is the persistent heat, with many locations reporting one of the hottest weeks (seven consecutive days) on record, including:

  • Las Vegas: hottest week with an average of 115.4, better than 115.1 in 2005.
  • Bishop, California: hottest week with an average high of 108.4, up from 107.4 in 2021.
  • Medford: second hottest week with an average of 106.4, after 108.4 in 1981.
  • Palm Springs: fourth hottest week with an average high of 117.7.

DC recorded the fourth hottest five-day period on record, with an average temperature of 31.4 degrees Celsius.

The climate connection

Scientific studies have shown that human-induced climate change increases the intensity, frequency and extent of heat waves.

According to the Climate Shift Index from science communications firm Climate Central, the likelihood of recent high temperatures due to human-caused climate change is four to five times higher across much of the West and two to three times higher in the Mid-Atlantic region and Northeastern United States.

The planet is currently experiencing 13 consecutive months of record-breaking warm temperatures, and in the United States it is the second warmest year on record.

Jason Samenow contributed to this report.

By Everly