Salt Lake City, Utah, experienced its warmest meteorological winter – December through February – in 152 years of record-keeping, according to preliminary data. This marks a striking trend across much of the western United States, where record-high temperatures dominated what is traditionally the coldest season.
A large area stretching from Southern California to the High Plains and Northern Rockies registered its warmest winter on record, based on 131 years of climate data. While the contiguous United States as a whole recorded its second-warmest meteorological winter, cooler temperatures in the eastern half of the country prevented it from surpassing the all-time record. Several other cities joined Salt Lake City in claiming winter 2025-26 as their warmest on record, including Tucson, Arizona (130 years of data) and Rapid City, South Dakota (114 years of data). Phoenix, Arizona, exceeded its previous record – set just last year – by nearly 3 degrees.
The mild winter wasn’t solely defined by temperature. The Midwestern Regional Climate Center’s Accumulated Winter Season Severity Index (AWSSI), which factors in both temperature and snowfall, indicates record mild conditions across the West. The AWSSI considers the entire period with meteorological winter characteristics, meaning “winter” may still be ongoing for some locations even as March begins.
The lack of snowfall accompanying the warmer temperatures is a significant concern. Diminished snowpack has ripple effects as the region transitions into warmer months, impacting water resources and potentially contributing to drought conditions.
The unusual warmth is linked to a persistent ridge of high pressure over the western United States. This ridge forced the jet stream to steer storms northward, limiting snowfall in the mountains and allowing warmer air to dominate. This pattern is associated with a negative phase of the Arctic Oscillation (AO), a global atmospheric circulation pattern. A weaker polar vortex, characteristic of a negative AO phase, allows cold air to spill into the eastern U.S. While trapping warmer air over the West.
“When the AO is in a negative phase, the polar vortex is weaker, which allows for colder air to spill into the eastern half of the country while trapping the western half under warmer conditions,” explained Sara Tonks, a content meteorologist with weather.com, who holds degrees in Earth and Atmospheric Sciences and Marine Science.
The National Weather Service’s Winter 2025-26 Outlook, released prior to the season, did not predict the extent of the warmth ultimately experienced. The Old Farmer’s Almanac’s spring 2026 forecast, released in late 2025, also did not anticipate the record-breaking winter conditions.