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March 2026 was the warmest March on record for the contiguous U.S., characterized by a historic snow drought in the West and extreme heat that increased cooling energy demand. Globally, the month was the second-warmest on record, with Arctic sea-ice reaching a near-record low maximum. In the U.S., severe drought affected 77% of the contiguous region, while Hawaii experienced record-breaking precipitation due to Kona lows.

In January 2026, the United States experienced an average temperature anomaly of -1.2°F, with 133 cities recording cooler-than-average conditions. Despite this national trend, the western U.S., particularly the Northern Rockies & Plains, saw significant warming, with Helena, Montana, recording the highest anomaly at 9.1°F. Long-term data indicates that 191 of the 194 analyzed cities have experienced warming trends since 1970, with Great Falls, Montana, showing the largest increase of 9.6°F. Climate attribution analysis using the Climate Shift Index (CSI) highlighted that San Juan, Puerto Rico, had 24 days where temperatures were at least five times more likely due to climate change.

February 2026 was the fifth-warmest month globally on record, with the contiguous U.S. experiencing its second-warmest winter in 132 years. A critical 'snow drought' affected the western U.S., where snow-covered areas in January were only 34% of normal, threatening water supplies for agriculture and energy. Climate Central's analysis indicates that human-driven climate change significantly influenced winter temperatures, particularly in the Southwest, and is the primary cause of spring warming in 98% of 241 examined U.S. cities.

The report finds that while December 2025 temperatures in the U.S. were evenly split between warmer-than-average and cooler-than-average cities, long-term trends show nearly all analyzed cities have warmed since 1970. The Southwest was the most unusually hot region, with Casper, Wyoming, recording the highest anomaly. Climate signal (CSI) was minimal nationwide, though San Juan, Puerto Rico, saw 10 days where temperatures were at least five times more likely due to climate change.

The report analyzes 22 extreme weather events in 2025, noting that despite weak La Nina conditions, global temperatures remained exceptionally high due to human-driven emissions. It emphasizes that warming of approximately 1.3°C has intensified heatwaves, droughts, and floods, with a specific focus on how women and marginalized groups bear a disproportionate burden. The document also identifies a critical gap in climate science, where a lack of observational data in the Global South hinders confident analysis of rainfall events. Finally, it argues that while adaptation is necessary, events like Hurricane Melissa in the Caribbean demonstrate that adaptation has limits and cannot replace the urgent need for rapid emission reductions.

The document reports that 2025 is virtually certain to be among the top five hottest years globally, driven by rising carbon pollution from fossil fuels. In the U.S., record high temperatures significantly outpaced record lows, and the year saw a record-costly start for billion-dollar weather and climate disasters, including the most expensive wildfire event on record in Los Angeles. Globally, carbon pollution intensified Hurricane Melissa, which devastated Jamaica. The report also highlights a trend of 'hydroclimate whiplash' contributing to both the Los Angeles fires and deadly flash floods in Texas, while noting that the U.S. has rolled back key clean energy policies and is set to withdraw from the Paris Agreement by January 2026.

In November 2025, the United States experienced an average temperature anomaly of 2.1°F across 194 analyzed cities, with the western half of the country seeing exclusively above-average temperatures. The Southwest, South, and Northern Rockies and Plains were the most unusually hot regions, with anomalies exceeding 4.8°F. Waco, Texas, recorded the highest anomaly at 7.5°F. Long-term trends show 183 of 194 stations have warmed since 1970, with El Paso, Texas, seeing the greatest increase of 6.9°F. Climate attribution via the Climate Shift Index (CSI) highlighted San Juan, Puerto Rico, with 27 days at CSI 5, meaning temperatures were at least five times more likely due to climate change.

The document reports that November 2025 was the third warmest on record globally and the fourth warmest for the contiguous U.S. It highlights a long-term trend of warming winters in the U.S., where the coldest day of the year has warmed by approximately 7°F since 1970. The briefing also notes significant regional anomalies, such as extreme warmth in Texas and heavy rainfall in southern California, while discussing the ongoing La Niña advisory and its expected impacts on weather patterns through early 2026.

In October 2025, the United States experienced an average temperature anomaly of 2.0°F across 192 analyzed cities, with the Ohio Valley seeing the most unusual heat at 4.89°F above normal. Fairbanks, AK, recorded the highest individual city anomaly at 7.1°F. Long-term data indicates that 190 of 191 analyzed stations have shown positive warming trends since 1970, with Wheeling, WV, experiencing the fastest increase at 7.8°F. Climate change influence was particularly strong in San Juan, PR, which had 29 days at a Climate Shift Index (CSI) of 5, and Honolulu, HI, where both cities saw at least two weeks of CSI values of 2 or higher.

The report finds that 86% of analyzed global marathons will see a decline in the odds of optimal running conditions by 2045. While elite women are more resilient to heat, elite men are most affected, particularly at the Tokyo Marathon, which is projected to see the largest decline in ideal conditions among the Abbott World Marathon Majors. The analysis highlights that the 2025 Tokyo and Berlin Marathons experienced unusual heat made two to three times more likely by climate change. Shifting race start times to sunrise is identified as a potential adaptation to increase the likelihood of optimal temperatures for most runners.

The document explains that rising global temperatures increase 'atmospheric thirst,' where the atmosphere absorbs more moisture from the land. In the western U.S., this heat-driven demand has replaced lack of precipitation as the leading cause of exceptional drought since 2000, contributing to a multi-decade megadrought in the Southwest and increasing wildfire risk in California and Nevada.

The October 2025 briefing reports that global temperatures remained exceptionally high, with the month ranking as the third warmest on record. In the U.S., warming fall temperatures have delayed the first freeze in 88% of analyzed cities, while significant drought persists across 67% of the contiguous U.S. despite localized heavy rainfall in Southern California.

Between June and August 2025, human-induced climate change significantly increased global temperatures, with at least 22% of the global population experiencing temperatures at Climate Shift Index (CSI) level 2 or higher every day. Nearly 955 million people faced 30 or more 'risky heat days' added by climate change, with the highest impact seen in Asia. The report also documents severe climate-driven events, including record rainfall and flooding in China, India, Pakistan, and the U.S., as well as historic wildfires in Europe and Canada.

Climate Central's analysis for June to August 2025 reveals that at least 22% of the global population experienced temperatures made at least twice as likely by climate change daily. In the U.S., over 21 million people in 32 cities faced 30 or more 'risky heat' days added by climate change, with some cities, such as Honolulu, seeing all their risky heat days attributed to human-caused warming.

The 2025 fire season in Spain and Portugal saw extreme burned areas, with Spain experiencing its worst fires in 30 years and Portugal burning 260,000 ha. These events coincided with the most intense heatwave on record in Spain. Analysis indicates that a 1.3°C increase in global temperatures since preindustrial times has made these extreme fire-conducive weather conditions approximately 40 times more likely, transforming an event that would have occurred once every 500 years into one expected every 15 years.

August 2025 in the United States was generally cooler than normal, with an average anomaly of -0.5°F across 196 cities, though 189 of those cities have shown long-term August warming trends since 1970. Despite the monthly average, 27 cities experienced at least two weeks of Climate Shift Index (CSI) values of 2 or higher, and San Juan, Puerto Rico, saw 28 days at CSI 5, indicating a strong climate change influence on those specific days.

Japan and South Korea experienced extreme summer heat in 2025, with Japan recording its hottest June and July in 127 years. The Climate Shift Index (CSI) indicates that human-caused climate change made these events at least five times more likely, with several cities experiencing over a month of CSI level 5 temperatures.

A forecast for extreme heat across the Southwest U.S. and northern Mexico indicates temperatures up to 18°F above normal, with the Climate Shift Index (CSI) attributing a level 5 likelihood to human-caused climate change. Approximately 53 million people are expected to be affected by these conditions, which are compounded by persistent drought in the region.

In July 2025, the United States experienced an average temperature anomaly of 1.4°F across 196 analyzed cities, with the eastern half of the country seeing above-average temperatures. The Ohio Valley was the most unusually hot region, while the West was the only region cooler than normal. Long-term data indicates that 189 of the 196 cities have seen warming trends since 1970, with Reno, Nevada, experiencing the most significant increase. Climate change influence was particularly strong in the Southeast and in San Juan, Puerto Rico, where 19 days reached a Climate Shift Index (CSI) of 5.

An analysis of 240 UK cities from 1970 to 2024 shows that 85% have experienced an increase in the average number of days per year exceeding 27°C. In cities such as Cambridge, Luton, and Bedford, the average number of such days rose from 1 per year in the early 1970s to 11-13 per year between 2020 and 2024, with human-caused climate change responsible for the majority of this increase.