Blistering conditions will build on Friday and throughout the weekend in the central and southern parts of California, where many residents should prepare for the hottest weather of the year, the National Weather Service (NWS) warned on Thursday.
Midday highs were mostly expected to be above 38 degrees Celsius (100 Fahrenheit), and desert areas could reach 49C (120F), forecasters said.
Heatwaves, which can be deadly, are occurring more frequently across North America as its summer unfolds from June through September — and as the world sees more extreme weather patterns that scientists link to climate change.
An excessive heat watch was in effect through Sunday in California for interior Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties on Thursday.
“Please plan accordingly, this is not the time to be hiking or be outside for long durations,” the Los Angeles branch of the NWS said on Twitter. “If you need to work outside, shift hours to the early morning, take frequent breaks and hydrate!”
Employers were reminded to adhere to regulations that require outdoor workers to be given water, shade and regular breaks to cool off.
The state will be performing spot checks at work sites to make sure the rules are being followed, said Jeff Killip of California’s Division of Occupational Safety and Health.
Across the US, more than 111 million people were under extreme heat advisories, watches and warnings, mostly in the Southwest, the NWS reported on Wednesday.
Forecasters said the long-duration heatwave is extremely dangerous, especially for the elderly, the homeless and other vulnerable populations. The heat could persist into next week as a high-pressure dome moves west from Texas. In Arizona, temperatures have hit 43C (110F) for more than a dozen consecutive days.
Horse-racing events were cancelled at the California State Fair near the state capital Sacramento over concerns for animal safety.
Meanwhile, California’s wildfire season was ramping up amid the hot, dry conditions as a series of blazes erupted across the state this week, according to Secretary Wade Crowfoot of the California Natural Resources Agency.
“As we get deeper into the summer and vegetation that grew up during the wet spring dries out, we are seeing an uptick in wildfire activity,” Crowfoot said on Wednesday during a state media briefing.
Crowfoot added that global climate change was “supercharging” heatwaves. California has instituted a $400m extreme heat action plan to protect workers, help vulnerable communities and assist local communities in opening cooling centres.
The plan, announced last year as an update to state recommendations made a decade earlier, has a broad range of near- and long-term goals.
Elements include increasing public awareness through targeted communication, statewide public health monitoring to identify heat illness events early on, and developing codes and regulations to protect everything from schools to water supplies from extreme heat.
Officials said the state’s power system, which was strained to the point of widespread blackouts in recent years, has been fortified and should be able to withstand the latest heatwave.
The California Independent System Operator, which runs the electricity grid, said battery storage capacity reached 5,600 megawatts on July 1 — enough to power more than 3.8 million homes for up to four hours before recharging.
“The batteries being added to the grid are charged during the day, when solar power is abundant, and dispatched primarily in the evening hours when demand is still high and the sun is setting and solar capacity diminishing,” the system operator said in a statement.
As the US Southwest endures an ongoing heatwave, the Northeast has seen intense flooding this week.
“Make no mistake, the devastation and flooding we’re experiencing across Vermont is historic and catastrophic,” Vermont Governor Phil Scott said on Wednesday.
The state, whose capital Montpelier closed its downtown because of the flooding, is bracing for more heavy rain in the coming days.