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Data

Hottest day of the year over land, relative to 1961–1990 (ERA5, IGCC 2025)

How hot the hottest day of the year gets over land: each place's highest daily maximum temperature of the year, averaged over all land except Antarctica, as the difference from its 1961–1990 average, each year from 1950. From the ERA5 reanalysis (a weather model constrained by observations, not a direct measurement; values before the satellite era rest on fewer observations), as calculated by Indicators of Global Climate Change 2025. It measures intensity, how hot the hottest day is, not how often extremes happen, and it shows the change without attributing it to a cause. IGCC adds a single 0.51 °C to express it relative to 1850–1900; that is not added here. IGCC's Berkeley Earth and HadEX3 versions are not included: they are not coverage-matched with ERA5, Berkeley Earth's terms are non-commercial, and HadEX3 ends in 2018.

Latest value

1.30°C

Land, excluding Antarctica (average over all ERA5 land grid points), 2025. Version IGCC-2025a.

Hottest day of the year over land, relative to 1961–1990 (ERA5, IGCC 2025) (degrees Celsius)

76 values from 1950 to 2025.
Show as a table
Hottest day of the year over land, relative to 1961–1990 (ERA5, IGCC 2025), every value
PeriodValue (°C)Status
1950−0.89final
1951−0.47final
1952−0.18final
1953−0.13final
1954−0.37final
1955−0.19final
1956−0.50final
1957−0.17final
1958−0.10final
1959−0.17final
1960−0.17final
19610.08final
1962−0.30final
1963−0.04final
1964−0.19final
1965−0.46final
1966−0.21final
1967−0.24final
1968−0.16final
19690.25final
19700.09final
1971−0.15final
1972−0.05final
19730.20final
1974−0.40final
19750.01final
1976−0.41final
1977−0.07final
1978−0.20final
19790.09final
19800.16final
19810.17final
1982−0.16final
19830.47final
1984−0.01final
1985−0.18final
1986−0.07final
19870.28final
19880.74final
19890.33final
19900.45final
19910.54final
1992−0.04final
1993−0.23final
19940.44final
19950.53final
19960.11final
19970.21final
19980.99final
19990.50final
20000.42final
20010.63final
20020.85final
20030.76final
20040.44final
20050.92final
20060.85final
20070.94final
20080.58final
20090.56final
20101.33final
20110.82final
20121.02final
20130.94final
20140.93final
20151.10final
20161.18final
20171.15final
20181.19final
20191.40final
20201.43final
20211.46final
20221.31final
20231.78final
20241.84final
20251.30final
Indicators of Global Climate Change 2025: Forster et al. (2026), Earth Syst. Sci. Data 18, 3889–3933, doi:10.5194/essd-18-3889-2026; data: Smith et al. (2026), version IGCC-2025a, doi:10.5281/zenodo.21494229. CC BY 4.0. CC BY 4.0.

Where it comes from

Producer
Indicators of Global Climate Change (IGCC) consortium, led by the University of Leeds · Indicators of Global Climate Change 2025
Version
IGCC-2025a
File
https://zenodo.org/api/records/21494229/files/ClimateIndicator/data-IGCC-2025a.zip/content
Fetched
2026-10-04 (automatically), 1,495,354 bytes
Fingerprint
sha256 04658ff91053808aced03f65dc977311668aec1610ec83bec72fff303dcbcbcd
Copies
Archived copy (Wayback Machine) Our copy of the exact file
Cite the producer
Forster, P. M., Walsh, T., Smith, C., Lamb, W. F., Lamboll, R., Cassou, C., Hauser, M., Hausfather, Z., Lee, J.-Y., Palmer, M. D., von Schuckmann, K., Slangen, A. B. A., Szopa, S., Trewin, B., Yun, J., Gillett, N. P., Jenkins, S., Matthews, H. D., Raghavan, K., Ribes, A., Rogelj, J., Rosen, D., Zhang, X., Allen, M., Andrew, R. M., Atkinson, C., Betts, R. A., Bombelli, A., Burgess, S. N., Cheng, L., Claxton, H. E., Friedlingstein, P., Frölicher, T. L., Domingues, C. M., Gasser, T., Gregory, C. H., Hoesly, R. M., Huppmann, D., Ishii, M., Kadow, C., Karwat, A., Kennedy, J., Killick, R. E., Kovilakam, M. V. M., Krummel, P. B., Lan, X., Lamarque, J.-F., Liné, A., Martín-Míguez, B., Monselesan, D. P., Morice, C., Mühle, J., Mussak, P., Peters, G. P., Pirani, A., Pongratz, J., Rigby, M., Rohde, R., Savita, A., Seneviratne, S. I., Smith, S. J., Taha, G., Tassone, C., Thorne, P., Wells, C., Western, L. M., van der Werf, G. R., Wijffels, S. E., Zecchetto, M., Zhong, J., Zhang, X.-Y., Masson-Delmotte, V., and Zhai, P.: Indicators of Global Climate Change 2025: annual update of key indicators of the state of the climate system and human influence, Earth Syst. Sci. Data, 18, 3889–3933, https://doi.org/10.5194/essd-18-3889-2026, 2026. Smith, C., Walsh, T., Gillett, N., Hauser, M., Krummel, P., Lamb, W., Lamboll, R., Mühle, J., Palmer, M., Ribes, A., Schumacher, D., Seneviratne, S., Slangen, A., Trewin, B., von Schuckmann, K., & Forster, P. (2026). Indicators of Global Climate Change 2025 (Version IGCC-2025a) [Computer software]. Zenodo. https://doi.org/10.5281/ZENODO.21494229
Producer
Indicators of Global Climate Change (IGCC) consortium, led by the University of Leeds · Indicators of Global Climate Change 2025
Version
IGCC-2025a
File
https://essd.copernicus.org/articles/18/3889/2026/essd-18-3889-2026.pdf
Fetched
2026-10-04 (automatically), 9,736,703 bytes
Fingerprint
sha256 795eb30a2ed5defdffb78499b0c3eac2314eac3a4ab5d7e9f093bef336acafebETag "9491ff-653ed6ee5a83f" · Last-Modified Wed, 10 Jun 2026 22:04:53 GMT
Copies
Archived copy (Wayback Machine) Our copy of the exact file
Cite the producer
Forster, P. M., Walsh, T., Smith, C., Lamb, W. F., Lamboll, R., Cassou, C., Hauser, M., Hausfather, Z., Lee, J.-Y., Palmer, M. D., von Schuckmann, K., Slangen, A. B. A., Szopa, S., Trewin, B., Yun, J., Gillett, N. P., Jenkins, S., Matthews, H. D., Raghavan, K., Ribes, A., Rogelj, J., Rosen, D., Zhang, X., Allen, M., Andrew, R. M., Atkinson, C., Betts, R. A., Bombelli, A., Burgess, S. N., Cheng, L., Claxton, H. E., Friedlingstein, P., Frölicher, T. L., Domingues, C. M., Gasser, T., Gregory, C. H., Hoesly, R. M., Huppmann, D., Ishii, M., Kadow, C., Karwat, A., Kennedy, J., Killick, R. E., Kovilakam, M. V. M., Krummel, P. B., Lan, X., Lamarque, J.-F., Liné, A., Martín-Míguez, B., Monselesan, D. P., Morice, C., Mühle, J., Mussak, P., Peters, G. P., Pirani, A., Pongratz, J., Rigby, M., Rohde, R., Savita, A., Seneviratne, S. I., Smith, S. J., Taha, G., Tassone, C., Thorne, P., Wells, C., Western, L. M., van der Werf, G. R., Wijffels, S. E., Zecchetto, M., Zhong, J., Zhang, X.-Y., Masson-Delmotte, V., and Zhai, P.: Indicators of Global Climate Change 2025: annual update of key indicators of the state of the climate system and human influence, Earth Syst. Sci. Data, 18, 3889–3933, https://doi.org/10.5194/essd-18-3889-2026, 2026. Smith, C., Walsh, T., Gillett, N., Hauser, M., Krummel, P., Lamb, W., Lamboll, R., Mühle, J., Palmer, M., Ribes, A., Schumacher, D., Seneviratne, S., Slangen, A., Trewin, B., von Schuckmann, K., & Forster, P. (2026). Indicators of Global Climate Change 2025 (Version IGCC-2025a) [Computer software]. Zenodo. https://doi.org/10.5281/ZENODO.21494229
Producer
Indicators of Global Climate Change (IGCC) consortium, led by the University of Leeds · Indicators of Global Climate Change 2025
Version
IGCC-2025a
File
https://raw.githubusercontent.com/ClimateIndicator/data/0f2765dc2e96c98aebceb78fb12cd28fcfb9ac6f/data/base/extreme_temperatures/txx_timeseries.csv
Fetched
2026-10-12 (automatically), 2,431 bytes
Fingerprint
sha256 c93fc6f4fff8f6665b8dd8aa446eabb4de74378596f8393004e2c6f2223c94a4ETag W/"043ff4ac6f40d70e27df66de4877b9ac5c72db34715f7afda7f5a3df91a43ad0"
Copies
Archived copy (Wayback Machine) Our copy of the exact file
Cite the producer
Forster, P. M., Walsh, T., Smith, C., Lamb, W. F., Lamboll, R., Cassou, C., Hauser, M., Hausfather, Z., Lee, J.-Y., Palmer, M. D., von Schuckmann, K., Slangen, A. B. A., Szopa, S., Trewin, B., Yun, J., Gillett, N. P., Jenkins, S., Matthews, H. D., Raghavan, K., Ribes, A., Rogelj, J., Rosen, D., Zhang, X., Allen, M., Andrew, R. M., Atkinson, C., Betts, R. A., Bombelli, A., Burgess, S. N., Cheng, L., Claxton, H. E., Friedlingstein, P., Frölicher, T. L., Domingues, C. M., Gasser, T., Gregory, C. H., Hoesly, R. M., Huppmann, D., Ishii, M., Kadow, C., Karwat, A., Kennedy, J., Killick, R. E., Kovilakam, M. V. M., Krummel, P. B., Lan, X., Lamarque, J.-F., Liné, A., Martín-Míguez, B., Monselesan, D. P., Morice, C., Mühle, J., Mussak, P., Peters, G. P., Pirani, A., Pongratz, J., Rigby, M., Rohde, R., Savita, A., Seneviratne, S. I., Smith, S. J., Taha, G., Tassone, C., Thorne, P., Wells, C., Western, L. M., van der Werf, G. R., Wijffels, S. E., Zecchetto, M., Zhong, J., Zhang, X.-Y., Masson-Delmotte, V., and Zhai, P.: Indicators of Global Climate Change 2025: annual update of key indicators of the state of the climate system and human influence, Earth Syst. Sci. Data, 18, 3889–3933, https://doi.org/10.5194/essd-18-3889-2026, 2026. Smith, C., Walsh, T., Gillett, N., Hauser, M., Krummel, P., Lamb, W., Lamboll, R., Mühle, J., Palmer, M., Ribes, A., Schumacher, D., Seneviratne, S., Slangen, A., Trewin, B., von Schuckmann, K., & Forster, P. (2026). Indicators of Global Climate Change 2025 (Version IGCC-2025a) [Computer software]. Zenodo. https://doi.org/10.5281/ZENODO.21494229

What was done to it

  1. Checked that each file read (txx_timeseries.csv) is byte-identical to the same path inside the IGCC-2025a release zip deposited on Zenodo (doi:10.5281/zenodo.21494229, sha256 04658ff91053…).

    Code: pipeline/src/envdash/transforms/climate/igcc_2025.py · code sha256 bb168888d911761a… · inputs 04658ff91053… 795eb30a2ed5… c93fc6f4fff8…

  2. Read the ERA5 column of txx_timeseries.csv: the land average (excluding Antarctica) of each grid cell's highest daily maximum temperature of the year, as an anomaly relative to 1961–1990 (°C), 1950–2025, as printed. The Berkeley column (Berkeley Earth's non-commercial terms) and the HadEX3 column (ends in 2018) are not used; the three are not coverage-matched and are never combined.

    Code: pipeline/src/envdash/transforms/climate/igcc_2025.py · code sha256 bb168888d911761a… · inputs 04658ff91053… 795eb30a2ed5… c93fc6f4fff8…

  3. Checked against the paper (Forster et al. 2026, Sect. 10.1, page 23 of the PDF snapshot, sha256 795eb30a2ed5…), whose statements were found in its text before publishing: the base period is 1961–1990, and the ERA5 mean over those years is 0.001 °C, zero to the file's two decimals; IGCC adds a single offset of 0.51 °C to express TXx relative to 1850–1900, which is not applied here; and its 2025 value relative to 1850–1900 and fall from the year before equal the file's values plus that offset and their difference, exactly.

    Code: pipeline/src/envdash/transforms/climate/igcc_2025.py · code sha256 bb168888d911761a… · inputs 04658ff91053… 795eb30a2ed5… c93fc6f4fff8…

What it covers

Geography
Land, excluding Antarctica (average over all ERA5 land grid points)
Baseline
1961–1990 mean of this series, as published by IGCC
Basis
Annual maximum of the daily maximum temperature (TXx) in each grid cell, averaged over land. ERA5 reanalysis (Copernicus Climate Change Service, ECMWF), processed by IGCC (M. Hauser, D. Schumacher and S. Seneviratne, ETH Zürich). Anomalies relative to 1961–1990 as published; IGCC's single offset to 1850–1900 is not applied.
Unit
degrees Celsius (°C)