People Exposed to Climate Change: December 2024 to February 2025

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KEY CONCEPTS

• Climate Central’s new global analysis shows where people felt the strongest influence of human-caused climate change on daily average temperatures between December 2024 and February 2025.

• Globally, at least one in five people felt a strong climate change influence every day during the last three months.

• In the U.S., more than 71 million people experienced at least two weeks’ worth of days with temperatures made at least twice as likely due to climate change.

• Fourteen U.S. cities — primarily located in western regions of the country — experienced at least three weeks’ worth of days with average temperatures made at least twice as likely by climate change.

• Alaska experienced the largest departure from its normal winter temperatures: 6.9°F warmer than its seasonal average. 

Global fingerprints of climate change

According to Climate Central’s latest report, People Exposed to Climate Change: December 2024 to February 2025, the effects of carbon pollution (mainly from burning coal, oil, and methane gas) influenced temperatures in nearly all regions of the world during the past three months.

This Climate Central analysis used the Climate Shift Index (CSI) to quantify the influence of human-caused climate change on daily average temperatures experienced in 220 countries and 940 cities — including 247 U.S. cities — during meteorological winter in the Northern Hemisphere (December 1, 2024 to February 28, 2025). See Methodology for details.

This analysis focuses on the average person’s experience of unusually warm conditions with a  strong influence of climate change (CSI level 2 or higher) during this period.

• A CSI level 2 (3, 4, etc.) indicates local temperatures that were made at least two (three, four, etc.) times more likely due to climate change.

• Learn more about the CSI: explore the map tool, watch a video explainer, or read the FAQs.

Globally, at least one in five people felt a strong climate change influence on temperatures every day from December 2024 to February 2025, according to Climate Central’s analysis.

• Explore interactive maps for countries and cities across six continents.

Warm winter days influenced by climate change in the U.S.

In the U.S., more than 71 million people experienced at least two weeks’ worth of days with temperatures made at least twice as likely due to climate change (CSI level 2 or higher).

In 17 U.S. states, the average person experienced warmer-than-normal temperatures this winter compared to the 1991-2020 seasonal average. 

• The average person in these states experienced between one (Mississippi) and 76 (Hawaii) winter days with temperatures made at least twice as likely due to climate change.

• Explore interactive maps for more data on U.S. states and cities.

This winter, 38% of U.S. cities analyzed (94 of 247) experienced average temperatures that were warmer than normal, compared to their 1991-2020 seasonal average.

In 14 U.S. cities — primarily located in western regions of the country — the average person experienced at least three weeks’ worth of days with average temperatures made at least twice as likely by climate change. 

• All 14 of these cities experienced a warmer-than-normal winter, ranging from 1.5°F (Salinas and San Francisco, California) to 7.6°F (Anchorage, Alaska) warmer than their 1991-2020 seasonal average. 

Table 1. U.S. cities with the most total days at CSI 2 or higher from December 1, 2024, to February 28, 2025, along with average temperature anomalies during this period.

Unusual winter warmth felt most strongly beyond the contiguous U.S.

• Alaska experienced the largest departure from its normal winter temperatures: 6.9°F warmer than its seasonal average. Three of the four U.S. cities with the highest departures from normal winter temperatures were in Alaska, with average temperatures that ranged from 4.1°F (Juneau) to 8.4°F (Fairbanks) warmer than normal. Anchorage and Juneau experienced among the most total days with a strong influence of climate change (51 and 47 respectively).

• San Juan, Puerto Rico saw the most days with a strong influence of climate change (CSI 2 or higher) among all U.S. cities during the last three months: 89 days. The island city experienced an average seasonal temperature that was 1.7°F warmer than normal.

• Honolulu, Hawaii saw the second-most days with a strong influence of climate change this winter (77 days) and experienced an average seasonal temperature that was 1.8°F warmer than normal during this past winter.

Year-round effects of warmer winters

Winter is the fastest-warming season for most of the U.S., and unusually warm winter days now happen more often. Winter warming has year-round effects that can:

• Contribute to longer growing seasons and longer allergy seasons.

• Increase the likelihood of ice-free lakes — which can influence lake water levels and lake-effect snow and have cascading impacts on cultural heritage, ecosystems, and recreation.

• Disrupt the chill that valuable fruit and nut crops depend on.

• Change the timing, location, and amount of snowfall — as well as spring snowmelt and water supplies.

• Decrease home heating demand, which can be offset by longer, higher cooling demand during warm seasons. 

LOCAL STORY ANGLES

Is climate change influencing daily heat extremes in your local area?

Climate Central’s Climate Shift Index (CSI) system provides tools, data, custom maps, and local alerts to answer this question in real-time. Here are three ways to use the CSI:

• Use the tools. Climate Central’s Climate Shift Index map tool shows which parts of the world are experiencing high CSI levels, every day. Explore the global CSI map for today, tomorrow, and any day in the recent past.

• Access KML to create custom CSI maps. The CSI is now available in KML format. Fill out this form to join our pilot project, receive the KML links, and create custom maps.

• Sign up for alerts. Sign up here to receive custom email alerts when strong CSI levels are detected in your local area.

CONTACT EXPERTS

To request an interview with a Climate Central scientist about this analysis, please contact Peter Girard at pgirard@climatecentral.org. 

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. 

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

All Climate Shift Index (CSI) levels reported in this brief are based on daily average temperatures and ECMWF ERA5 data from December 1, 2024 to February 28, 2025. See the frequently asked questions for details on computing the Climate Shift Index, including a summary of the multi-model approach described in Gilford et al. (2022).

Values shown in maps and tables across this website have been rounded for clarity. For exact data values, please download the full dataset above.

A detailed methodology can be found in the full report.