Climate Change Drove Record Winter Warmth in the Western U.S.

Between December 2025 and February 2026, human-caused climate change significantly influenced global temperatures, with more than one in six people daily experiencing temperatures at least twice as likely due to climate change. In the United States, a sharp divide occurred: western states saw record-breaking warmth, with nine states experiencing their warmest December-February on record and Casper, Wyoming, recording the highest temperature anomaly globally among 960 analyzed cities. Conversely, the eastern U.S. faced below-average temperatures and cold snaps that the Climate Shift Index (CSI) indicates were made less likely by climate change. The record warmth in the west has led to low snowpack in Oregon, Colorado, and Utah, threatening water supplies and increasing wildfire risks.

• From December 2025 to February 2026, over one-sixth of the global population experienced daily average temperatures that were at least two times more likely to occur because of human-caused climate change.
• The western United States experienced exceptional winter warmth, with nine states recording their warmest December-February period on record. Wyoming, Colorado, Montana, and Utah saw average temperatures more than 7°F above normal, with Wyoming reaching 9.3°F above normal.
• Among 960 cities analyzed globally, the western U.S. dominated the highest temperature anomalies, with 13 of the top 15 cities located there. Casper, Wyoming, had the highest anomaly at 13.0°F.
• Climate change increased the likelihood of unusually warm temperatures for residents in Hawaii, Arizona, California, Nevada, and New Mexico, who experienced more than a month of such conditions. In 54 U.S. cities, residents experienced at least two weeks of temperatures made at least two times more likely by climate change.
• The record-low snowpack in Utah, Colorado, and Oregon resulting from the warm winter threatens regional water supplies and may increase the intensity of wildfires due to drier grasslands and forests.
• While the eastern U.S. experienced below-average temperatures and extreme cold snaps, these events were generally made less likely by climate change. For example, a January 25, 2026, cold snap affecting 34 eastern cities was at least two times less likely to occur due to heat-trapping pollution.

APA

Climate Central (2026). Climate Change Drove Record Winter Warmth in the Western U.S. https://www.climatecentral.org/climate-matters/2025-us-winter-attribution

Chicago

Climate Central. Climate Change Drove Record Winter Warmth in the Western U.S. 2026. https://www.climatecentral.org/climate-matters/2025-us-winter-attribution.

Wikipedia

{{cite report |author=Climate Central |title=Climate Change Drove Record Winter Warmth in the Western U.S. |date=18 March 2026 |url=https://www.climatecentral.org/climate-matters/2025-us-winter-attribution |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climatecentral2026climate, author = {{Climate Central}}, title = {{Climate Change Drove Record Winter Warmth in the Western U.S.}}, institution = {Climate Central}, year = {2026}, month = mar, url = {https://www.climatecentral.org/climate-matters/2025-us-winter-attribution}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }