Climate Matters•January 31, 2024
Warmest Winter Days
KEY CONCEPTS
Winter is the fastest-warming season for most of the U.S., and unusually warm winter days now happen more often.
Most (86%) of the 240 U.S. locations analyzed by Climate Central now experience more very warm winter days than in the 1970s.
The rise in very warm winter days was highest in the Upper Midwest, Southeast, and Northeast.
Warming winters have year-round effects — on seasonal allergies, fruit and nut crops, water supplies, winter sports, and more.
Download data: Change in warmest winter days, 1970-2023 (240 locations)
Winter is warming — fast.
The most rapid warming in the U.S. has generally occurred when and where it’s coldest, including at night, in northern parts of the country—and during winter.
Winter (December, January, February) is the fastest warming season for the majority (74%) of U.S. locations analyzed by Climate Central.
Locations with the fastest winter warming since 1970 are found from coast to coast, but especially in the Northeast and the Great Lakes region.
More unusually warm winter days
The warming season is also reflected in the growing number of unusually warm winter days.
According to NOAA’s Climate Extremes Index, over the last 30 years (1994-2023), winter maximum temperatures have been exceptionally warm for 20% of the contiguous U.S. (about double the expected rate in a stable climate) and exceptionally cool for only 3% of the U.S.
New Climate Central analysis shows similar shifts toward exceptional winter warmth at the local level.
Using data from 240 U.S. weather stations, Climate Central analyzed the change in the number of winter days with unusually warm temperatures since 1970. Unusually warm winter days are defined as days at or above the upper tenth percentile of the local daily maximum temperature distribution during winters from 1970 to 2023 (see Methodology).
Since 1970, the average number of unusually warm winter days has increased in 206 (86%) of the 240 locations analyzed.
On average, these 206 locations now experience five more extremely warm winter days than they did in 1970s.
The rise in warmest winter days was above-average among stations in the Upper Midwest, Southeast, and Northeast.
The Upper Midwest and Northeast have a high concentration of ski areas that may be affected by more extremely warm winter days.
Learn more: On Thin Ice: How Climate Change is Shaping Winter Recreation
Explore: February temperatures in the 19 cities to host the Winter Olympics since 1950 have warmed by 4.8 °F on average since 1950.
The following cities saw the largest increase in unusually warm winter days since 1970:
Location | Unusually warm winter days threshold (°F) | Change in unusually warm winter days, 1970-2023 |
Miami, Fla. | 83° | +22 days |
Beaumont, Texas | 77° | +12 days |
Chico, Calif. | 68° | +11 days |
McAllen, Texas | 86° | +11 days |
Baton Rouge, La. | 77° | +10 days |
Flint, Mich. | 47° | +10 days |
Milwaukee, Wisc. | 45° | +10 days |
San Jose, Calif. | 67° | +10 days |
West Palm Beach, Fla. | 83° | +10 days |
Download data for all 240 locations.
Out of 240 stations analyzed, only 22 (9%) now experience fewer unusually warm winter days than in 1970. These stations were concentrated in the western U.S. — especially across the Northwest, Idaho in particular.
In a warming world there are…
Still freezing nights — but fewer of them.
The annual number of freezing nights has dropped in 204 U.S. locations from 1970 to 2022.
The average change across these 204 locations was 13 fewer freezing nights.
Still cold snaps — but shorter ones.
From 1970 to 2021, 97% of 244 U.S. locations analyzed experienced shrinking winter cold snaps.
Cold snaps shrank by 6 days on average across all 244 stations from 1970 to 2021.
Still extremely cold days — but not as cold.
Since 1970, the coldest day of the year has warmed by 7°F on average across 242 U.S. locations analyzed by Climate Central.
Yearly coldest temperatures rose at least 1°F in 97% of locations across every U.S. region.
Winter warming has year-round effects:
Contributes to longer growing seasons and longer allergy seasons.
Disrupts the chill that valuable fruit and nut crops depend on.
Changes the timing, location, and amount of snowfall — as well as spring snowmelt and water supplies.
Decreases home heating demand, which can be offset by longer, higher cooling demand during warm seasons.
Allows mosquitos to thrive: annual mosquito days have risen with temperatures across the U.S.
Can have serious consequences for cold-weather sports in the U.S. and around the world.
LOCAL STORY ANGLES
Did climate change influence local temperatures today?
Climate Central’s Climate Shift Index map tool shows the influence of climate change on daily low, average, and high temperatures. The Climate Shift Index is now available in KML format. Fill out this form to receive KML links and start creating custom maps. Sign up here to receive custom email alerts when a strong influence of climate change on temperatures in your area is detected.
FIND EXPERTS
Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts.
Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.
Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices.
Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area.
METHODOLOGY
Climate Central assessed local long-term trends (1970-2023) in the annual number of unusually warm winter days. This analysis defines an unusually warm winter day as any day during meteorological winter (December, January, February) with a maximum temperature at or above the 90th percentile. The 90th percentile was calculated based on all winter daily maximum temperatures from the start of winter 1970 (12/1/1969) through the end of winter 2023 (2/28/2023). Data were obtained from the Applied Climate Information System for 247 weather stations. For reported data summaries based on linear trends, however, only 240 stations are included due to data completeness measures that were not met by seven stations: Bend, Ore.; Dothan, Ala.; Hattiesburg, Miss., Hazard, Ky; Panama City, Fla.; Terre Haute, Ind.; and Wheeling, W.Va.