Monthly climate report
Climate report: September 2025
Global land temperature (NASA GISTEMP v4) and atmospheric CO₂: where things stand at the end of September 2025.
Global temperature in September 2025
- September 2025 (land)
- +2.05 °Cversus 1901–1930
- Rank of the month
- 2ndof 146 Septembers on record
- 2025, January–September
- +2.00 °C2nd of 146 years
- 12-month average
- +2.05 °C12 months ending September 2025
In September 2025, land areas worldwide were +2.05 °C warmer than the 1901–1930 average, according to NASA's GISTEMP v4 analysis, compared with +1.95 °C in September 2024. That makes it the 2nd warmest September in 146 years of records. The record for this month remains September 2023 (+2.48 °C).
From January to September, 2025 averages +2.00 °C — the 2nd warmest start to a year since 1880.
Over the 12 months ending in September 2025, the land average is +2.05 °C, against +2.16 °C over the previous 12 months. The highest 12-month average remains the one ending in August 2024 (+2.21 °C).
These figures cover land areas only. Land warms faster than the ocean, so the values are higher than the combined land-and-ocean averages usually quoted.
The last 13 months
| Month | Anomaly vs 1901–1930 |
|---|---|
| September 2025 | +2.05 °C |
| August 2025 | +1.78 °C |
| July 2025 | +1.44 °C |
| June 2025 | +1.69 °C |
| May 2025 | +1.70 °C |
| April 2025 | +2.23 °C |
| March 2025 | +2.53 °C |
| February 2025 | +2.07 °C |
| January 2025 | +2.56 °C |
| December 2024 | +2.38 °C |
| November 2024 | +2.01 °C |
| October 2024 | +2.16 °C |
| September 2024 | +1.95 °C |
The 10 warmest Septembers on record
Land areas, 1880–2025.
| # | Year | Anomaly vs 1901–1930 |
|---|---|---|
| 1 | September 2023 | +2.48 °C |
| 2 | September 2025this report | +2.05 °C |
| 3 | September 2024 | +1.95 °C |
| 4 | September 2020 | +1.71 °C |
| 5 | September 2021 | +1.59 °C |
| 6 | September 2019 | +1.53 °C |
| 7 | September 2022 | +1.43 °C |
| 8 | September 2005 | +1.42 °C |
| 9 | September 2016 | +1.42 °C |
| 10 | September 2013 | +1.38 °C |
Atmospheric CO₂
The annual mean rose from 421.08 ppm in 2023 to 424.60 ppm in 2024, +3.5 ppm in one year.
Sources and method
- Temperatures: NASA GISS, GISTEMP v4, monthly mean over land areas, rebased to 1901–1930 (file of November 14, 2026).
- Ranks use the months known at the date of the report. NASA slightly revises past values at each update, so figures can move by a few hundredths of a degree.
- CO₂: NOAA Global Monitoring Laboratory, Mauna Loa Observatory.