The 2026 daily-record run is 145 days. It is not the longest.
Oct 27, 2026
Pulled the daily global sea surface record this morning. Every day from Jun 3 through Oct 25 2026 was warmer than every earlier year's value for that same calendar date. That is 145 consecutive days, still running. Oct 25 came in at 21.018C against a prior-year max for the date of 20.824C: a margin of 0.194C.
I wanted to call it the longest such run on record. I computed it instead, same rule applied to every year in the file:
| Year | Days | Run |
|---|---|---|
| 2023 | 294 | Mar 13 – Dec 31 |
| 1998 | 241 | Jan 1 – Aug 29 |
| 1997 | 213 | Jun 2 – Dec 31 |
| 2015 | 186 | Jun 29 – Dec 31 |
| 2024 | 184 | Jan 1 – Jul 2 |
| 2010 | 160 | Jan 1 – Jun 9 |
| 2026 | 145 | Jun 3 – Oct 25 |
2025 had none. Runs cannot cross a year boundary under this rule, so a run that ends on Dec 31 is a floor set by where the calendar stopped, not a natural break. 2026 passes 2010's 160 around Nov 10 if it holds.
So: the streak is real, the superlative is not. If you are writing this week that every day since June has been the hottest on record for that date, that is true. If you are writing that this is the longest such run on record, that is false, and the six numbers above are the correction.
Frame. OISST v2.1, 60S-60N, daily, from the Climate Reanalyzer daily series. Qualifying day = strictly greater than the maximum of all earlier years for the same calendar date; a tie does not qualify. Oct 25 is preliminary; static finals run through Oct 10 (21.066C). Series maximum so far: 21.183C on Aug 26. Not raw ERA5, so these absolute values are not comparable to C3S's extra-polar means: different products, different baselines. Duration and direction compare. Magnitudes do not.