Monthly Attribution Overview – January 2026

An analysis of how climate change boosted United States temperatures in January 2026

Using Climate Central’s Climate Shift Index (CSI) tool to measure the impact of climate change on daily temperatures across the United States, as well as NOAA’s Applied Climate Information System (ACIS) to find daily temperature information, we have compiled a high-level overview of how climate change has affected temperature trends in January in cities across the United States. (Dataset downloadable as Excel workbook here.)

1. High-Level Findings

• Overall, the U.S. saw below-average temperatures in January, with an average anomaly — or difference from normal — of -1.2°F across 194 cities.

• While much of the country experienced colder-than-usual conditions, the western U.S. stood out with a notably warm January, contrasting sharply with below-average temperatures across large parts of the central and eastern U.S.

• Five cities experienced one of their top five warmest January temperatures on record. On average, stations have data reaching back to 1893.

• Elevated Climate Shift Index values were observed across the U.S. in the  Northern Rockies & Plains, Southwest, and West.

• Although January 2026 was cooler than average, long-term January warming trends show that nearly all cities analyzed have warmed since 1970, consistent with findings from Climate Central’s 2025 Winter Package.

Figure 1. Threaded ACIS temperature anomalies (differences from normal) for January 2026 relative to the 1991-2020 normal. Analysis based on ACIS data.

Figure 2. Days with a CSI of 2 or higher for January 2026 for ACIS threaded stations. Analysis based on ERA5 data.

2. Local Temperature Anomaly Analysis

• The average temperature anomaly — or difference from normal — across the 194 cities analyzed was -1.2°F. 

• January temperatures skewed colder: 57 cities recorded warmer-than-average conditions, while 133 cities experienced cooler-than-average temperatures. The remaining two cities saw near-normal January temperatures (0.0°F anomaly).

• Despite the national cold tilt, temperatures were elevated across many areas in the Northern Rockies & Plains, Southwest, and Western U.S.. The most unusually warm region was the Northern Rockies & Plains, where average temperature anomalies exceeded 3.3°F. 

• Twelve cities experienced their top 10 hottest Januaries on record.

• In contrast, cities in the Northwest, South, Southeast, Ohio Valley, and Upper Midwest experienced cooler-than-average temperatures. The most unusually cold region was the Ohio Valley, with average temperature anomalies of -3.9°F. 

• The most unusually warm city in January was Helena, Mont., which was 9.1°F warmer than usual. 

• Of the 194 ACIS locations analyzed, nearly all (191) showed long-term warming trends for January, indicating that these cities have warmed on average since 1970.

• Great Falls, Mont., experienced the greatest increase, with average January temperatures 9.6°F warmer than in 1970.

Table 1. ACIS stations with the highest January 2026 temperature anomaly.

Table 2. ACIS stations with the fastest warming January since 1970.

3. Local Climate Shift Index Analysis

• San Juan, Puerto Rico, had 24 days at CSI 5 in January, indicating that temperatures on those days were made at least five times more likely because of climate change.

• Eight cities across the country experienced at least a week's worth of days at or above a CSI of 2.

• On average, cities in the West experienced the highest number of days (12)with a CSI of 2 or above.

Table 3. ACIS stations with the highest number of days at or above a CSI 2 during January 2026.

METHODOLOGY

Calculating the Climate Shift Index

All Climate Shift Index (CSI) levels reported in this brief are based on daily average temperatures and ERA5 data. 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).

City Analysis

We analyzed 194 Applied Climate Information System (ACIS) stations associated with U.S. cities. For each city, we found the CSI time series from the nearest 0.25° grid cell. We calculated the number of days at CSI levels 2, 3, 4, and 5. We used ACIS data to find the average monthly temperatures, temperature anomalies (compared to 1991-2020 normals), and precipitation information, and to derive average monthly warming trends for each city.

Regions

Regions are defined by the National Centers for Environmental Information climate regions.