ReportJune 2, 2025

Monthly Attribution Overview May 2025

An analysis of how climate change boosted United States temperatures in May 2025

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 May in cities across the United States. (Dataset downloadable as Excel workbook here.)

1. High Level Findings

Report: Monthly Attribution Overview May 2025 FG 1

Figure 1. Threaded ACIS temperature anomalies for May 2025 relative to the 1991-2020 standard normal period. Analysis based on ACIS data.

Report: Monthly Attribution Overview May 2025 FG 2

Figure 2. Days with a CSI of 2 or higher for May 2025 for ACIS threaded stations. Analysis based on ERA5 data (5/01 - 5/28) and GFS data (5/28-5/31).

2. Local Temperature Anomaly Analysis

City

State

Temperature Anomaly (°F)

Average Temperature (°F)

Warming Since 1970 (°F)

San Antonio

TX

3.98

80.48

4.2

Great Falls

MT

3.75

55.26

-1.6

Jacksonville

FL

3.73

78.63

2.3

West Palm Beach

FL

3.51

82.21

2.7

Gainesville

FL

3.43

78.44

0.8

Helena

MT

3.42

57.37

3.0

Houston

TX

3.26

80.61

4.7

Rapid City

SD

3.26

57.37

-1.4

Orlando

FL

3.24

80.58

1.9

Tampa

FL

3.15

82.60

4.3

Table 1. Top 10 ACIS stations with the highest May 2025 temperature anomaly.

City

State

Warming Since 1970 (°F)

Temperature Anomaly (°F)

Average Temperature (°F)

Reno

NV

7.2

2.68

63.03

El Paso

TX

6.9

0.71

76.11

Chattanooga

TN

5.6

-0.94

69.06

Albany

GA

5.5

1.56

76.85

Las Vegas

NV

5.3

1.60

78.90

Medford

OR

5.3

1.61

62.02

Tucson

AZ

5.3

0.73

77.53

Huntsville

AL

5.1

-0.85

70.50

Wheeling

WV

4.9

-1.56

59.69

Louisville

KY

4.8

-1.46

66.79

Table 2. Top 10 ACIS stations with the fastest warming May since 1970.

3. Local Climate Shift Index Analysis

City

State

Days at CSI = 2 or higher

Days at CSI = 5

Average Temperature (°F)

Temperature Anomaly (°F)

Honolulu

HI

31

21

80.23

2.08

San Juan

PR

26

11

81.19

-0.35

Fort Myers

FL

22

15

82.02

2.72

West Palm Beach

FL

21

17

82.21

3.51

Tampa

FL

20

8

82.60

3.15

Sarasota

FL

20

15

80.10

2.25

Miami

FL

19

15

82.37

2.32

Gainesville

FL

17

5

78.44

3.43

Anchorage

AK

15

1

47.52

-0.63

Victoria

TX

15

13

78.95

1.71

San Antonio

TX

14

6

80.48

3.98

Table 3. Top 10 ACIS stations with the highest number of days at or above a CSI of 3 during May 2025.

METHODS

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 191 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, and precipitation information, and to derive average monthly warming trends for each city.