Western heatwave crashing records

A historically severe September heatwave is baking the West, breaking hundreds of records, posing a danger to public health and pushing California’s power grid to the limit. Some records have been shattered by wide margins as the scorching air mass exacerbates the fire danger in the drought-stricken region.

California’s Independent System Operator (ISO) says the state’s electric grid is under heavy strain and warned consumers ‘‘to be prepared for possible outages’’.

‘‘As the state faces the hottest day in this prolonged, recordbreaking heatwave, grid conditions are expected to worsen,’’ the grid operator wrote in a news release. ‘‘If needed, ISO could order utilities to begin rotating power outages to maintain stability of the electric grid.’’

The agency, which declared an energy emergency alert, predicted an all-time historic high demand of 52,258 megawatts for yesterday afternoon, surpassing its previous record of 50,270 megawatts on July 24, 2004.

The heat is historic for both its duration and intensity, evidenced by long-standing monthly and alltime records that continue to be toppled. San Jose set an all-time high of 42.7 Celsius (109 degrees F) yesterday afternoon.

In Sacramento, the downtown district got to 45C on Tuesday, just a degree below an all-time record set on July 17, 1975, and four degrees hotter than the previous September record. Records there date back to 1877.

Sacramento was expected to jump to 46.1C, which would be both a monthly and all-time record as well as only the 11th time in the past 145 years that the city made it to 44C or higher.

‘‘This will be essentially the worst September heatwave on record, certainly in Northern California and arguably for the state overall,’’ said Daniel Swain, a climate scientist at UCLA. ‘‘By some metrics, it might be one of the worst heatwaves on record period in any month, given its duration and its extreme magnitude, especially in Northern California and especially in the Sacramento region.’’

A whopping 42 million Americans are under excessive heat warnings, including across most of California, northeast Arizona and southern Nevada.

The Great Basin, southern Idaho and western Utah are also under heat advisories. The excessive heat is also fuelling the risk for fast-moving fires.

A number of large wildfires have erupted over the last week in California, Oregon, Idaho and Montana.

AP Debbie Chang, left, and Kim Burrell, right, load bottled water into a cart to be distributed to people on the street in Sacramento, California, yesterday. The pair passed out water and snacks to those they find in need on the streets.