[REVISION HISTORY]

Southwest US heat wave, wildfire, and monsoon impacts

Updated 28 times since CLSTR started tracking revisions of this situation.

What changed

2026-09-10 00:02 UTC → 2026-09-10 22:20 UTC · added ~~removed~~

By ~~early September,~~ September 9, extreme heat and high humidity continued to impact the ~~Southwest, specifically Southern California~~ Southwest and ~~the Desert Southwest.~~ Southern California. In Southern California, health officials reported an increase in emergency visits for heat-related illnesses. Climate scientist Daniel Swain noted that absolute humidity levels in the region are near the ceiling of historical a high-pressure system from Arizona and offshore winds drove multiple temperature records. In Long ~~Beach,~~ Beach reached 107 degrees, surpassing its 2015 record, while Downtown Los Angeles tied a previous record of 105 degrees. Escondido recorded its hottest day since recordkeeping began in 1893, and other areas including Camarillo, Oxnard, Santa Barbara, and Santa Maria also reported temperatures above prior marks. The National Weather Service warned of a ‘very high heat ~~alert was issued as~~ risk’ for at least one more day. The heat has impacted local infrastructure, with the Torrance Unified School District reporting record-breaking classroom temperatures. In the San Francisco Bay Area, record-breaking heat ~~index~~ was ~~projected~~ accompanied by a smog alert due to ~~reach 117 degrees. City Health Officer Dr. Cliff Okada warned that high humidity would~~ unhealthy ozone concentrations and warnings of potential minor coastal flooding. To manage surging air conditioning demand and prevent ~~temperatures from dropping significantly after sunset, with heat indices potentially remaining at 80 degrees or higher past 9 p.m. Simultaneously,~~ power outages, the Los Angeles Department of Water and Power urged residents to conserve electricity. In the Desert Southwest, extreme heat warnings ~~were issued~~ remained in effect for parts of ~~the Desert Southwest,~~ Arizona, California, and Nevada, including the Las Vegas Valley, Death Valley National Park, Lake Mead, and Lake Havasu. Forecasts indicated temperatures between 106 and 112 degrees Fahrenheit, with high humidity driving ‘feels like’ temperatures between 105 and 117 degrees. Safety officials ~~issued warnings regarding lethal temperatures in car interiors and~~ advised residents to stay hydrated and remain in air-conditioned ~~environments. By September 8, conditions intensified as tropical moisture from the remnants~~ environments, warning of ~~Hurricane Marie combined with extreme heat in Southern California. The National Weather Service issued warnings for Los Angeles and Orange counties, with inland~~ lethal temperatures potentially reaching 108 to 113 degrees Fahrenheit. Experts noted that high dew points, comparable to tropical forests, impede the body’s ability to cool itself. In the San Francisco Bay Area, heat was accompanied by a ‘Spare the Air’ alert due to unhealthy ozone and smog, alongside warnings of minor coastal flooding near San Francisco, San Pablo, and Monterey bays. In the Desert Southwest, heat warnings for regions in ~~Arizona, California, and Nevada were scheduled to remain in effect through Friday evening.~~ car interiors.

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