Heat persists in the West. When will it start feeling like fall?

For 15 consecutive months, the planet has experienced record-breaking heat, per the National Oceanic and Atmospheric Administration.
In September, high temperatures persisted — breaking several heat records in the West, including in Phoenix and Denver. Unusually hot temperatures continue to plague the United States this fall, especially in the West.
Several cities in the West have reached temperatures above 100 degrees in Oct. Last week, Palm Springs hit 117 degrees, matching a record for the hottest day in Oct. in the U.S. ever, per Vox. Phoenix reached 113 degrees last week and San Jose reached 106.
Why is it so hot this fall? When will it start cooling off in the West? Here is what we know.
There are a combination of factors driving temperatures up in fall 2024. These factors include La Niña, a heat dome and climate change.
Winter 2024-25 will experience La Niña conditions.
During a La Niña cycle, amplified jet streams can carry, “drier and warmer conditions across the southwestern” U.S., per NOAA.
In northern regions of the country, temperatures typically dip below average as a result of La Niña.
Heat domes drive temperatures up by trapping hot air beneath a high-pressure atmosphere, per the U.S. Department of Agriculture.
The pressure system can block winds and clouds from forming within the dome, resulting in stagnant heat.
There is currently an “expansive” heat dome stretching across the Southwest and the West Coast, per USA Today.
Global warming is largely responsible for enduring heat, according to NOAA.
“As a result of global warming, summers are getting hotter across much of the U.S. West, and both the number of heat waves and the length of the heat wave season are increasing,” per NOAA.
A recent study from the U.S. Global Change Research Program found that 46 out of 50 major cities in the United States “experienced a statistically significant increase in heat wave frequency between the 1960s and 2020s.”
“The increase in the length of the heat wave season was significant in 44 locations.”’
Temperatures across the Western U.S. are forecasted to start cooling off by November. Heat will likely persist through mid-October, especially in Four Corners region — Utah, Arizona, Colorado and New Mexico.
“The October temperature outlook favors well above average temperatures across all of the central and western parts of the nation, in northern Alaska, in southern Florida, around the Great Lakes, and in the Northeast,” per NOAA. “The best odds for a warmer-than-average October are centered over the Four Corners region, where probabilities exceed 70%.”
The Pacific Southwest is forecasted to start dipping in mid-November while maintaining a near-average temperature of 61 degrees through the month, according to The Farmer’s Almanac.
Heat is expected to begin letting up in the Bay Area this week.
“There’s a light at the end of the tunnel. We’re tired of it too, but here’s some good news. All Excessive Heat Warnings have been downgraded to Heat Advisories (until 11 PM today), and the Heat Advisory for the coast is no longer in effect,” The National Weather Service for The Bay Area tweeted on Monday.
Other major cities in the west will experiences cooldowns within the next month. In Phoenix, temperatures are predicted to cool next week, per The Farmer’s Almanac.
In Denver, cooling is expected during the second half of the month, and in Las Vegas temperatures will begin dropping next week.
You can unpack your sweaters — cooler weather is on the horizon in Utah.
According to the Farmer’s Almanac 60-day forecast, temperatures in Salt Lake City should start cooling down during the second-half of October. By November, temperatures will get cold, with the average for the month being 39°.
“Winter will be warmer than normal, with the coldest periods in late November and late January,” per the Farmer’s Almanac.
Through Oct. 18, Utah has a 70% probability of experiencing above-average temperatures, per The National Weather Service Climate Prediction Center. By Oct. 19 and through the end of the month, chances of above-average temperatures drops to 50%.
Utah’s abnormal heat is the result of “a high-pressure setup over the Four Corners region,” which is, “minimizing cloud cover and allowing the state to heat up,” according to KSL meteorologist Devan Masciulli.
Warm air from the southwest is also blowing west right now and heating Utah.
Long-range forecasts from NOAA indicate normal to slightly below average precipitation levels across Utah for the remainder of the year.
Utah’s first snowfall of the season already arrived in September this year. Alta Ski Resort shared images of a light dusting of snow across the resort on Sept. 17, per X. The average day of first snowfall in the Utah valley is Nov. 8, as reported by KSL News.