Southern California braces for hottest weather so far this year
A dangerous heat wave is developing across California and the Desert Southwest as a large area of heat-trapping high pressure builds and expands into this weekend. Officials are urging people to protect against the dangers of extreme heat as temperatures in many locations are expected to soar past 100 degrees, in some places as much as 15 to 20 degrees above what’s typical for this time of year.
Excessive-heat warnings are in effect Wednesday through Friday across much of Southern California into far southern Nevada and southwest Arizona, while less severe heat advisories cover portions of central and Northern California into far southwest Oregon. The National Weather Service is forecasting “multiple days of widespread highs into the triple digits and maximum temperatures up to around 115-120F in the typically hottest desert locations.”
Los Angeles will probably see its longest, hottest stretch of the year thus far. In Southern California, only areas right along the coast will escape the intense heat, because of the cooling influence of the Pacific Ocean. Other hot spots will include Phoenix, Las Vegas and Death Valley, with highs in the upper 90s to low 100s expected to span much of interior California all the way north into southwest Oregon.
Some calendar-day records are possible in California, Nevada and Arizona, but the best chance of record heat is in western Oregon and portions of Washington state later this week. In Oregon, the cities of Portland, Salem, Eugene and Medford could all come close to or surpass their calendar-day records as highs reach the low 100s.
The September heat wave comes after much of the Western United States had its hottest summer on record. The heat should gradually ease this weekend as the expansive high-pressure heat dome slowly drifts east.
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Heat building in Southern California
The heat begins to build Tuesday in Southern California’s valleys, with afternoon highs generally between 95 and 105 degrees. Even hotter highs of 105 to 109 are expected Tuesday in the western San Fernando Valley, where an excessive-heat warning is already in effect for locations including Northridge, Woodland Hills, Van Nuys and Chatsworth.
Thursday looks to be the hottest day of the heat wave, with highs of 100 to 110 degrees across much of Southern California. “Kiln-like” temperatures near 113 are possible in the western San Fernando Valley, the Weather Service in Los Angeles said. Daytime highs in Los Angeles are forecast in the mid-90s to near 100 Wednesday through Friday and perhaps into Saturday, or about 15 degrees above average.
In Death Valley, one of the hottest places on Earth and getting hotter, highs of 115 to 118 are forecast for Tuesday through Saturday.
Officials are reminding people to never leave anyone alone in a closed car; drink plenty of water; use air conditioners and stay in the shade; and wear loosefitting, light-color clothing. “The homeless, elderly, children, and those with health issues are at the highest risk for heat illness,” the Weather Service in Los Angeles said.
Nighttime lows will provide only limited relief, with many interior areas dipping only into the 70s and some spots failing to fall below 80 degrees.
The heat, combined with very low humidity and areas of gusty winds, will lead to “an extended period of elevated to brief critical fire weather conditions across the valleys, foothills, mountains, deserts, and southwest Santa Barbara county,” the Weather Service said.
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In Las Vegas and Phoenix, the heat goes on
After enduring their hottest summer on record, there’s no letup in the heat for Phoenix and Las Vegas. Both cities are looking at highs well into the 100s this week, with daytime highs and nighttime lows about 5 to 10 degrees above average.
Phoenix is forecast to reach 108 to 114 degrees Tuesday through Saturday, with nighttime lows in the mid-80s to near 90. Those temperatures could push the Phoenix area to the highest levels of the Weather Service’s HeatRisk forecast, which rates the heat’s danger to human health. During the same period, Las Vegas is expecting highs near or above 105 degrees and lows in the low to mid-80s.
“Temperatures of these magnitudes in early September will cause HeatRisk levels to increase into the major to locally extreme category, meaning that most of the general population is under the risk of heat-related illnesses if the proper heat precautions are not taken,” the Weather Service in Phoenix said.
Phoenix is now on its longest streak of days reaching at least 100 degrees, while Las Vegas set summer records for the number of days that the high temperature exceeded 100, 105, 110 and 115 degrees, and the number of nights that the low temperature stayed above 90 and 80 degrees. Las Vegas recorded an all-time high of 120 degrees on July 7.
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Still warm next week
The high-pressure heat dome is forecast to subside by next week, reducing the threat for dangerously extreme heat. But temperatures are still expected to be significantly warmer than average across much of the western United States, according to the latest forecast from the Weather Service’s Climate Prediction Center.