The season’s first major heat wave in the Western United States will peak Thursday and Friday after already breaking records this week in California, the Desert Southwest and Texas. More than 30 million people across the region, which includes the metropolitan areas of Phoenix, Las Vegas and Sacramento, are under alerts for dangerously hot temperatures as officials urge residents to take precautions against heat illness.
With temperatures forecast to surge 15 to 20 degrees above normal, excessive heat warnings and heat advisories span much of California, western and southern Nevada, western and southern Arizona, and portions of Utah, New Mexico and southwestern Texas. In locations including Las Vegas, desert areas of southeastern California and southwestern Texas, the risk of extreme heat has registered at the highest level on the National Weather Service’s HeatRisk forecast, which rates the danger to human health.
Officials are recommending people limit their time outdoors during the hottest portion of the day, stay hydrated and have access to air conditioning. They are also reminding caregivers not to forget anyone in a hot car.
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The heat spread into the western U.S. from Mexico, which has suffered through a prolonged and deadly heat wave in recent weeks. Scientific analysis indicates the heat is being enhanced by human-caused climate change.
Records already broken
After several calendar-day records were set in Texas on Tuesday, including 111 degrees in San Angelo and 109 degrees in Del Rio, the heat expanded into Arizona and California on Wednesday. Calendar-day records on Wednesday included:
Many other locations in the Four Corners states and California recorded top-5 highs for the date, including 108 in Las Vegas, the city’s second-hottest high on record for June 5. Phoenix also reached 108, with the Central Valley of California soaring into the 100s as well.
On the East Coast, Florida continues to simmer. Fort Myers reached 98 on Wednesday, tying its record high for the date.
Extreme heat continues into the weekend
Forecasters expect the worst of the heat to focus on California’s Central Valley and the Desert Southwest from Thursday through Saturday.
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Temperatures were forecast to reach near 100 to 105, or nearly 15 degrees above normal, in the central California cities of Redding, Chico, Yuba City, Sacramento, Stockton and Modesto on Thursday and Friday, and near 110 in the San Joaquin Valley and nearby foothills. Much of the area was under a Level 3 HeatRisk, described as “major” heat that “affects anyone without effective cooling and/or adequate hydration.”
Las Vegas is predicted to be one of the hottest spots. The HeatRisk forecast was at a Level 4 through the three-day period, which is described as “rare and/or long-duration extreme heat with little to no overnight relief.” Portions of southwestern Texas were also at a Level 4 HeatRisk on Thursday before somewhat lower humidity was expected to lower the risk to Level 3 for Friday and the weekend.
Several major cities are in line for dangerous, record-challenging heat:
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- Death Valley, Calif., was forecast to reach near 123 on Thursday and Friday and 117 to 119 on Friday and Saturday. If the temperature hits 124, that would be the highest so early in the year.
- Las Vegas was forecast to reach a high near 112 on Thursday, which would be the earliest in the year the city has been that hot, and 108 to 111 on Friday and Saturday. The average high for this time of year is 97.
- Phoenix was poised for its hottest day so far this year on Thursday with a forecast high of 113, compared with an average high for the date of 102.
- Tucson was forecast to reach 107 to 108 on Thursday and Friday. Wednesday was the city’s first 105-degree day of the year, coming a few days ahead of schedule. On average, the city’s first such day occurs on June 11.
Other hot spots include South Texas, where the heat index was forecast to be up to 110 to 115 on Thursday; Albuquerque and Roswell in New Mexico, where high temperature should reach near and over 100; and Salt Lake City, which is expecting highs in the mid-90s through the weekend.
The coastal cities of San Francisco, Los Angeles and San Diego are cooler because of a marine influence, with daytime highs only in the 70s to near 80.
Forecast models show the heat easing across much of the Western United States by late in the weekend. But the Weather Service warned that “dangerous heat will then engulf much of the Great Basin and Intermountain West, and may persist into next week.”
Heat reaches top level of climate index
The ongoing heat wave is a direct result of a high-pressure heat dome that has scorched Mexico for weeks — resulting in the country’s hottest and driest May on record — before spreading north and west into portions of the United States this week. Such heat domes suppress clouds and compress the air beneath them, causing the air to heat up.
Climate Central’s Climate Shift Index also indicates an influence from human-caused climate change, with much of the Southwestern U.S. reaching a Level 5. That is the highest level of the index, indicating that human-caused climate change has made such heat five times as likely.
Ian Livingston contributed to this report.
