A broad dome of high pressure is driving a significant heat wave across the western United States, pushing temperatures into the 90s and low 100s from California’s Central Coast to the Rocky Mountains. In Colorado, the National Weather Service placed Denver, Boulder and Fort Collins under a heat advisory from 10 a.m. to 9 p.m. Wednesday, warning that the mercury could reach 100–102°F. The reading would challenge the city’s July 9 record of 101°F and mark Denver’s first triple-digit day of 2025. California faces similar extremes. The Bay Area’s interior valleys and the Sacramento Valley are forecast to hit 100–105°F on Thursday and Friday, while Southern California’s Inland Empire and high deserts could see up to 105°F through Friday, prompting heat alerts and the opening of cooling centers. Farther north, Reno and other western Nevada communities are bracing for highs above 100°F this weekend, and Salt Lake City recorded its second 100°F day of the year on Wednesday with hotter conditions expected Thursday. Meteorologists say temperatures are running 5–20°F above seasonal averages across the region and urge residents—especially older adults, children and those with medical conditions—to limit outdoor activity, stay hydrated and seek air-conditioned spaces.