A historic, long-lasting and intense heat wave is not over yet, but it has already broken dozens of records — including all-time milestones. It poses an ” extreme” health risk for tens of millions of people.

The big picture: The heat has expanded to affect nearly the entire western U.S., with warnings and advisories stretching from Las Vegas to Seattle.

• Nearly 75 million people , mainly in the West, are under some type of extreme heat warning or advisory on Sunday.
• In the West, though, a near-record-strong heat dome is yielding scorchingly hot and dry conditions, and raising wildfire risks. Multiple large and difficult-to-contain fires are already burning .
• Excessive heat warnings along the West Coast stretch from Nevada and Arizona through California and northward into Oregon and Washington State.

Zoom in: In California, temperatures have climbed to 20°F to 30°F above average during the holiday weekend, with highs reaching the upper 110s°F to low 120s°F in some inland and desert locations.

• Numerous daily, monthly and all-time heat records will fall this weekend as the heat peaks.
• Heat risk levels are high enough to endanger “anyone without effective cooling and/or adequate hydration,” per the National Weather Service.
• Forecasts call for the heat wave to continue through the coming week in many areas, which will cause health risks to spike.
• “A long-duration, rare, heat wave with an Extreme Heat Risk through late this week will have many impacts on all of our citizens and all sectors of the community,” the NWS forecast office in Hanford, Calif. stated in an online forecast discussion Sunday morning .

By the numbers: All-time record high temperatures in the East and the West show the potential for milestones to be set during this bi-coastal event.

• Las Vegas hit an all-time high temperature of 120°F on Sunday afternoon, beating by 3 degrees its previous record that was hit in 2021, 2017, 2013, 2005 and 1942, according to NWS’ local office . It is unusual for an all-time record to be broken by such a large margin .
• Death Valley, Calif. reached at least 129°F on Sunday , just 1-degree shy of the hottest reliably measured temperature on Earth.
• On Friday, Raleigh reached 106°F with a heat index of 118°F, setting records for its all-time hottest temperature and highest heat index. In the West, Palm Springs, Calif. reached 124°F, for an all-time high temperature record there too.
• On Saturday, Redding, Calif. topped out at 119°F, beating its old all-time record high of 118°F.

What’s next: More records are predicted to fall through midweek.

Context: Human-caused climate change , largely from burning fossil fuels such as coal and natural gas, has greatly increased the odds of heat waves and led them to become more intense and longer lasting , multiple studies show.

• Research shows that climate change is leading to larger, more frequent wildfires in the West, which are exhibiting more frequent instances of extreme behavior that makes them more difficult to contain.
• According to the Climate Shift Index from the research organization Climate Central, human-caused climate change is making daytime highs and overnight lows this weekend in much of inland California as well as parts of Oregon and Washington, among other areas, at least five times as likely to occur.
• This is compared to a preindustrial atmosphere without added amounts of planet-warming greenhouse gases. Such cities include Sacramento; Portland, Ore.; and Las Vegas.

Threat level: In California, red flag warnings are in effect for much of the state, which has been impacted by intense heat since Tuesday.

• Abundant vegetation that grew during the wet winter months has quickly dried out from the heat, reaching record dry levels for this time of year, particularly in northern California.
• This is greatly elevating wildfire risks. For example, the French Fire , located near Mariposa, Calif., prompted evacuations and road closures Thursday night.
• The Lake Fire in Santa Barbara County has already burned more than 13,000 acres.
• Record hot overnight minimum temperatures are helping to fuel this and other blazes .

Rebecca Falconer contributed reporting.

Editor ‘s note: This story has been updated with the latest conditions and Las Vegas’ temperature highs.