Monthly Attribution Overview – June 2026

An analysis of how climate change boosted United States temperatures in June 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 April in cities across the United States. (Dataset downloadable as an Excel workbook here.)

1. High-level findings

• Overall, the U.S. saw slightly above-average temperatures in June, with an average anomaly — or difference from normal — of 0.7°F across 192 cities.

• While much of the central and eastern U.S. experienced below-average temperatures, above-average temperatures were more common across the western U.S. and parts of the Northeast and Southeast.

• Eleven cities experienced one of their top five warmest June temperatures on record. On average, stations have data dating back to 1893.

• Elevated temperature anomalies — or differences from normal — occurred in six of the nine U.S. Climate Regions, including the Southwest, West, Northwest, Northeast, South, and Southeast.

• June 2026 experienced above-average temperatures, mirroring the long-term June warming trends, which show that nearly all cities analyzed have warmed since 1970, consistent with findings from Climate Central’s 2025 Summer Package. 

Figure 1. Temperature anomalies (differences from normal) for June 2026 relative to 1991-2020 normals. Analysis based on threaded ACIS station-level data.

Figure 2. Statewide average days with a CSI level 2 or higher for June 2026. Analysis based on ERA5 data.

2. Local temperature anomaly analysis

• The average temperature anomaly — or difference from normal — across the 192 cities analyzed was 0.7°F. 

• June temperatures leaned warm, with 122 cities recording warmer-than-average conditions, compared to 67 cities that experienced cooler-than-average conditions.

• Temperatures were elevated across many areas in the Southwest, West, Northwest, Northeast, South, and Southeast. The Southwest stood out as the warmest region, with average temperatures more than 2.9°F above normal. 

• Twenty-five cities experienced their top 10 hottest Junes on record.

• The most unusually warm city in June was Flagstaff, Arizona, which was 4.0°F warmer than usual.

• Of the 192 locations analyzed, most (189) showed long-term warming trends for June, indicating that these cities have warmed on average since 1970.

• Reno, Nevada, experienced the greatest increase, with average June temperatures 10.6°F warmer than in 1970.

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

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

3. Local Climate Shift Index analysis

• San Juan, Puerto Rico, had 30 days at or above CSI 2 in June, indicating that temperatures on those days were made at least two times more likely because of climate change.

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

• On average, cities in the Southwest experienced the highest number of days (14) with a CSI of 2 or above.

Table 3. ACIS stations with the highest number of days at or above CSI 2 during June 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 192 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 NOAA’s National Centers for Environmental Information climate regions.