An unprecedented heatwave is scorching parts of the western United States in early October, with record temperatures and excessive heat warnings expected to last into the weekend.
Forecasters say a sweltering late-season heatwave will bring a risk of moderate to extreme heat to parts of the Southwest this week and into the weekend. About 39 million people in the region were under heat warnings Wednesday, according to the National Weather Service.
The National Weather Service has issued excessive heat warnings for areas near major cities including Las Vegas, Phoenix, San Francisco and Los Angeles. High temperatures are expected to be 10 to 25 degrees above normal in parts of Arizona, California and Nevada, forecasters said.
“Similar areas will experience severe to extreme heat over the next few days, with temperatures rising in the 90s to 110s this afternoon, potentially leading to record high temperatures,” the National Weather Service said Wednesday. I warned you.
These hot conditions are caused by heat domes, which are strong high-pressure systems that trap heat across the region and prevent cold air from entering. AccuWeather meteorologist Isaac Longley told USA TODAY that a ridge of high pressure continues across the Southwest.
“Certainly, this is a very impressive range of heat for some places and cities, especially in the West and Southwest,” Longley said. “It’s not really moving. It’s not really affecting the jet stream enough to actually bring cooler, or at least more comfortable, weather to the Southwest and even areas along the West Coast.”
Longley also noted that the heat dome is “vast” and is affecting other areas, including Denver, with unseasonably warm temperatures. Forecasters said dozens of heat records were likely to be set across the Southwest and West Coast over the weekend.
The early fall heatwave comes after an extremely hot summer that hit both the western and eastern United States. The National Oceanic and Atmospheric Administration reported last month that the summer of 2024 was the country’s fourth warmest on record.
Several states, including Arizona and California, experienced their hottest summers on record, according to the National Oceanic and Atmospheric Administration (NOAA). NOAA’s Climate Prediction Center said, “As a result of global warming, summers are becoming hotter across much of the western United States, and both the number of heat waves and the length of the heat wave season are increasing.”
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Phoenix experienced its hottest summer on record this year, but there was little recovery in September, with temperatures continuing to exceed 100 degrees and even 110 degrees throughout the month.
Temperatures continue to set records well into October, reaching 113 degrees in both Phoenix and Yuma on Tuesday, making it the hottest October day in the city’s history. Until this week, Phoenix had never experienced temperatures above 110 degrees in October, according to National Weather Service forecasts.
According to the Arizona Republic, part of the USA TODAY Network, Phoenix had its eighth consecutive day of record-setting or record-breaking temperatures on Tuesday. The record attempts continued Wednesday, with the National Weather Service in Phoenix reporting temperatures reached 108 degrees, breaking the previous record of 107 degrees set in 1980.
The Bureau of Meteorology announced on Wednesday that the Bureau of Meteorology’s excessive heat warning had been extended into the weekend as “record daily high temperatures are expected to continue.” Temperatures in the lower desert region are expected to be between 105 degrees and 112 degrees.
Record temperatures in California
Temperatures reached seasonal highs in parts of the California coast, AccuWeather said. Temperatures soared to 94 degrees in San Francisco on Tuesday. According to the Bureau of Meteorology, it was the hottest day in the city since 2022.
“Yesterday it was 94 degrees in San Francisco, and today is expected to be the same,” the San Francisco Weather Bureau announced Wednesday. “For October, this benchmark has only been reached 15 times in the past 150 years.”
The National Weather Service extended an excessive heat warning for the interior of the Bay Area, the Central Coast and the city of San Francisco until late Thursday. Temperatures in San Jose reached 106 degrees on Wednesday, setting or recording a daily high for several days in the region and breaking previous records of 96 degrees set in 1980 and 2012, according to the weather service.
High temperatures will continue in Los Angeles through Thursday, with temperatures in the hottest areas potentially reaching 100 to 106 degrees, the National Weather Service said. Several records have already been set across Los Angeles County on Tuesday, with temperatures reaching triple digits in some cities.
According to AccuWeather, temperatures this week are expected to be 5 to 10 degrees warmer than historical averages.
Contributors: Skylar Heisey and Hayleigh Evans, Arizona Republic