A historic heat wave is sweeping through the western U.S., pushing October temperatures to unprecedented levels as human-induced climate change extends extreme heat well into fall. Many cities are experiencing record-breaking highs, with some still seeing temperatures in the triple digits.
On Tuesday, Palm Springs reached a scorching 117°F, while Phoenix recorded 113°F and Tucson hit 105°F. In California, San Jose set a new daily high at 100°F, Oakland reached 96°F, and San Francisco hit 94°F, marking its hottest October temperature in two years. Some areas are expected to see even higher temperatures by Wednesday, with heat warnings issued across California, Arizona, and Nevada. Cities like San Francisco, Las Vegas, and Phoenix are under excessive heat warnings, while Los Angeles faces a heat advisory.
The extreme heat is set to move east, potentially breaking records in Colorado, where Denver could see temperatures hit 90°F, the latest occurrence of such heat in the city’s history. This record heat is expected to persist through the weekend, amplifying the risk of fires across regions from California to Montana due to dry, hot, and windy conditions.
Climate experts attribute the growing intensity and frequency of heat waves to climate change. The number of heat waves in major U.S. cities has doubled since the 1980s, according to the federal government’s Fifth National Climate Assessment. Human-driven climate change has made record-breaking temperatures like those seen in Palm Springs and Phoenix five times more likely, as per Climate Central’s Climate Shift Index.
Additionally, global warming is extending extreme heat into fall, with average nighttime fall temperatures in U.S. cities rising by 2.7°F between 1970 and 2023, especially in the Southwest.
