A National Weather Service mapping tool that shows which parts of the country are facing imminent heat danger has bad news for California. Starting Tuesday and lasting through the weekend, much of the state is expected to see “major” or “extreme” levels of heat risk.

The hot weather expected this week is “anomalous and potentially dangerous,” the National Weather Service said in an update Monday.

Numerous heat records are expected to be broken statewide.

One way the federal weather agency tracks heat danger is with its interactive HeatRisk map. It categorizes heat-related dangers into five risk levels: none, minor, moderate, major and extreme.

By Wednesday, a huge swath of the state – from Redding down to Los Angeles County – will be in the worst two categories. It gets even hotter on Thursday, where only a few coastal communities will be spared.

The dangerous heat persists in most places on Friday and Saturday before improving slightly on Sunday.

Heat risk is deemed major or extreme (shown in red and purple on the HeatRisk map) when it’s so hot that it poses a risk to people’s health, especially those without air conditioning at home. About a quarter of households in the state don’t have AC, the Sacramento Bee reported in 2022.

But air conditioning only works if you have power. Parts of the Bay Area and Northern California were warned that their power could be shut off to reduce the risk of wildfire amid the high temperatures and gusty winds.

Excessive heat warnings were issued for parts of Los Angeles County and are expected to stay in place for a full week. Sacramento is expected to stay above 100 degrees all week and get as hot as 110 at times.

110 will be the norm for Fresno and Bakersfield, who have highs between 110 and 112 five days in a row. Desert communities near San Diego could even see it reach 117 degrees. Even San Francisco, which tends to stay cool, could reach the 90s.

“The duration of this heat wave is concerning as the current forecast keeps scorching conditions in place through at least the end of the week,” the National Weather Service said Monday.

Back-to-back hot days, with little overnight cooling, are especially dangerous to people’s health.

“This level of heat could pose a danger to the entire population if proper heat safety is not followed,” the agency continued. Experts advise staying out of the sun, staying hydrated and checking on vulnerable neighbors and loved ones.

California isn’t alone in facing this heat. On Monday, the National Weather Service said over 50 million residents nationwide were under heat-related watches, warnings, and advisories.