California faces down worst heatwave of year amid threat of blackouts

Extreme heat is also raising wildfire risks as a late-summer ‘heat dome’ hits

An extended and dangerous heatwave is hitting the western US this week, with potentially record-breaking temperatures.

High temperatures could put stress on California’s electrical system, warned the state grid operator, as energy demands rise, largely due to air conditioning needs. Over the weekend, when temperatures are supposed to be hottest, electricity conservation may be necessary to avoid outages, they added.

By the weekend, high temperatures are forecasted to reach above or near 110 degrees Fahrenheit (43 degrees Celsius) in much of southern California, the Central Valley, Arizona and Nevada.

Already on Wednesday, temperatures were forecast to shoot up to around or well above 100F (38C) across the region, and heat will build over the next few days. In some areas, daily highs could reach up to 115F (46C).

The extreme temperatures in this “prolonged and possibly record” late-summer heatwave could be dangerous for human health, especially as high temperatures overnight will provide “little relief”, according to the National Weather Service (NWS).

On Monday — the Labor Day holiday — heat is expected to be at its worst. Sacramento, California is forecast to reach 113F (45C) by midday. The hottest temperature ever recorded in the city is 114F (46C).

The rest of the Central Valley will also be extremely hot on Monday, between the 107F (42C) expected in Bakersfield to the 111F (44C) expected in Stockton, Chico and Redding. Downtown Los Angeles is forecast to reach around 100F (38C), while parts of the San Fernando Valley and Inland Empire could reach well over 110F (43C).

High temperatures will hover at or just below 110F (43C) in much of western Arizona, including Phoenix, and southern Nevada, including Las Vegas, for the rest of the week and into the weekend.

Temperatures are also expected to hit around 100F (38C) on Wednesday and Friday in much of eastern Oregon and Washington, as well as parts of Idaho.

An “excessive heat warning” has been issued for most of California, as well as parts of Nevada and Arizona. Other parts of California, Washington, Oregon, Nevada and Idaho are under “excessive heat watch” or “heat advisory.”

The heatwave is being driven by a “heat dome”, meaning a contained bubble of hot air that can linger over an area for days.

The NWS office in Sacramento has warned people to stay vigilant on these heat extremes throughout the week, stay hydrated and seek air conditioning.

Temperatures this high can be incredibly dangerous, especially to people like the elderly, young children and those with pre-existing health conditions. Heat-related illnesses can run from sunburns and heat rash to potentially fatal heat stroke, where the body is unable to cool itself down.

The heatwave is also bringing renewed wildfire danger to the region, as low humidity and constant heat can be a boon to sparks and flames. Multiple fires are already burning in the western US, including two in Yosemite National Park in California’s Sierra Nevada Mountains.

In western Oregon, the Rum Creek and Cedar Creek fires have burned almost 13,000 acres and 8,000 acres, respectively, while remaining mostly uncontained.

Wildfire risk is even further exacerbated by the ongoing and devastating drought out West, which has dried out vegetation and made the wilderness prime for burning.l

Heatwaves like this are expected to become more common and even hotter as the climate crisis grows.

The world has already warmed about 1.1-1.2C above 19th-century temperatures. If the world reached 2C of warming, heatwaves that once occurred every 10 years would happen about once every other year, and be 2.6C hotter, according to the United Nations’ Intergovernmental Panel on Climate Change.