Californians are bracing for the first major heatwave of the year, a multiday scorcher that could bring triple-digit temperatures, pose significant threats to public health and sharply heighten wildfire risks.
After a notably cooler summer, temperatures are expected to spike across the American south-west starting on Wednesday and extending through the weekend, as severe conditions expand north along the coast into British Columbia by the end of the week.
The extreme weather event will create a trio of compounding dangers, with a heightened chance of thunderstorms also predicted alongside the heat and fire risks.
The National Weather Service has issued a swath of heat advisories, watches and warnings, along with red-flag alerts, warning the public to prepare.
“This dangerous level of heat will pose a threat to anyone without effective cooling and adequate hydration,” NWS forecasters said in an outlook issued on Wednesday, outlining temperature highs that could climb past 110F (43C) in the desert south-west and above 100F across southern California.
Temperatures could break local daily records in Los Angeles and across Arizona and Nevada. The heat will also linger after the sun sets, offering little reprieve overnight. “Widespread record warm overnight minimum temperatures” are possible through the west, according to climate scientist Daniel Swain, who shared an analysis of the upcoming event on his website.
High night-time temperatures will add challenges to containing fires that erupt and increase the dangers for people unable to access cooling. “This heatwave may be most notable for sustained overnight warmth in some cases,” Swain said, “with minimum temperatures not dropping below 70-80F.”
August is typically hot across this region. But for Californians who have not acclimated to high temperatures this year, the sharp shift could create health challenges. Those facing the greatest hazards will be outdoor workers, unhoused people and vulnerable populations, including children and seniors.
Extreme heat, often called a “silent killer”, already ranks as the most lethal weather-related disaster in the US, and deaths are increasing. Fueled by the climate crisis, and often exacerbated by concrete cityscapes that cook when temperatures rise, heatwaves are getting longer, larger and more intense.
Many areas that will be affected by this week’s heat event were also already primed to burn, including across areas of Los Angeles and Ventura counties. An extreme lack of moisture across southern California this year has left hillsides parched, overgrown and prone to ignite. But the heat could further cure vegetation, setting the stage for rapid fire growth and extreme behavior, according to the NWS.
“California wildfire risk will likely reach its peak during this event between Thursday and Saturday,” Swain said. While these fires are not expected to be amplified by strong gusty winds, developing thunderstorms could add erratic breezy conditions and lightning could ignite new blazes.
To prepare for the added threats, California’s governor, Gavin Newsom, has pre-deployed resources into high-risk areas, including 32 fire engines, nine water tenders, nine bulldozers, five helicopters, nine hand crews, 13 dispatchers and two incident management teams.
It has already been a busy year of fire across the country, and more than 44,400 blazes have ignited, roughly 16% higher than the 10-year average. But there are still months to go before the highest risks typically subside, especially in California where strong Santa Ana winds blow through the autumn months.
