CNN
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Millions of people in the West are experiencing a dangerous and historic October heatwave with temperatures so extreme they’d be considered hot during the peak of summer.
The heat has been so potent the United States soared to and tied the highest temperature ever seen in the month of October on Tuesday.
At least 125 places from the West Coast to the Rockies have tied or broken all-time October heat records since the month began. Many others have set daily high temperature records.
It’s another reminder that extreme heat is no longer confined to the summer as the world warms due to fossil fuel pollution.
“Climate change is causing the length of the heat season to increase and is making… fall heat waves like this more frequent,” Kristina Dahl, a climate scientist with the Union of Concerned Scientists said. “If we continue to warm the plant by burning fossil fuels, late-season heat waves like this will become much more common.”
California has been at the epicenter of the extreme heat.
Palm Springs soared to 117 degrees on Tuesday and tied the all-time highest October temperature on record for the entire US. It was the hottest reading in the country this late in the year in more than 40 years.
A few locations have been hotter this week than during the summer.
San Jose, California, was one. Thermometers in the city topped out at 102 degrees on July 2, but hit an astounding 106 degrees on Wednesday – 5 degrees higher than the city’s previous warmest October day.
The record-breaking heat began before the calendar flipped to October. Last weekend was part of a sizzling stretch of record-breaking conditions in Las Vegas and Phoenix – two cities where heat has been especially brutal this year.
Five consecutive days of record-breaking September heat in Las Vegas peaked with 104 degree readings on Saturday and Sunday. It was the hottest the city has even been so late in the year.
The heat was and continues to be even more severe and exceptional in Phoenix, which is in the middle of nine consecutive days of record-breaking high temperatures. The city recorded its second-warmest September day when it hit 117 degrees on Saturday, a mark never hit so late in the month. It then had its hottest October day on record Tuesday, topping out at 113 degrees. Wednesday marked the 113th day this year temperatures in Phoenix were at or above 105 degrees – another all-time record.
Phoenix is in Arizona’s Maricopa County where officials say heat was responsible for more than 300 deaths this year. Hundreds of additional potential heat-related deaths are still under investigation, according to the county.
Heat is the deadliest form of extreme weather and climate change is making heat waves more severe, long-lasting and possible at any time of the year. It’s especially dangerous when it fails to cool down enough overnight – another symptom of climate change.
The heat has not been limited to the Southwest and California. Dozens of Colorado cities, including Denver, have set or tied all-time October temperature records since Tuesday. Denver tied its all-time October record on Wednesday when the city hit 89 degrees – the hottest it’s been this late in the year.
The worst of the heat just peaked for much of the Southwest and parts of the Rockies, but seriously hot conditions will stick around through early next week.
More than 30 million people in the West are still under heat alerts – including 18 million under excessive heat warnings. Nearly 200 additional high temperature records and record-warm low temperatures could be set through the weekend from California to the Rockies.
“Dangerously hot temperatures will be common across many valley, mountain, and inland areas,” the National Weather Service in Los Angeles warned Thursday, underscoring the heat’s wide reach.
Highs in the upper 90s to near 100 degrees are forecast in Sacramento through at least Sunday. California’s capital spent the first two days of the month mired in the July-like triple digits.
Even coastal areas, often resistant to the heat, won’t escape it this time. Temperatures will gradually climb in Los Angeles through the weekend and into early next week. By Monday, a high temperature in the low 80s is possible, which could be one of the 10-warmest days of the year.
Phoenix could reach two consecutive weeks of record-breaking heat as it remains stuck in it into at least midweek.
And Denver will climb back into the 80s on Friday and highs will continue to surpass that threshold through at least the middle of next week.
The heat will also increase the risk of dangerous wildfires – especially in California.
“Dry heat like this essentially sucks moisture out of plants and turns them into dry tinder for a wildfire should a spark ignite,” Dahl explained.
A heat wave baked California about a month ago and destructive fires like the Line Fire and Bridge Fire took advantage, roaring to life not long after. Santa Ana wind season typically gets underway in October and could drive fire concerns to the extreme once these violent winds meet tinder-dry conditions.
