NOAA National Centers for Environmental Information

NOAA Daily Optimum Interpolation Sea Surface Temperature (OISST), version 2.1

Daily sea-surface temperature on a global 0.25° grid from 1 September 1981, blending AVHRR satellite data with ship, buoy and Argo float measurements and filling gaps by optimum interpolation. Each daily file also carries an anomaly (its metadata says "Climatology is based on 1971-2000 OI.v2 SST"), an error estimate and sea-ice concentration. Files for roughly the last two weeks are preliminary and are replaced by final files; the site keeps that status and labels those days preliminary.

Free to reuse with creditactiveUS federal programmeFetched automatically

Numbers published from it

None yet: this source is registered and its licence checked, and its numbers are being prepared.

Licence and credit

Licence: Public domain (work of the US federal government)
What the terms say: “publicly available, and no restrictions are placed upon their use.”
From the producer's terms, checked 2026-10-04; re-checked automatically every week.
Credit we give: NOAA National Centers for Environmental Information, OISST version 2.1 (Huang et al.), doi:10.25921/RE9P-PT57, accessed {date_accessed}.
Copy of the raw file: Allowed: we keep a public copy of every version we use.
Cite as: Huang, Boyin; Liu, Chunying; Banzon, Viva F.; Freeman, Eric; Graham, Garrett; Hankins, William; Smith, Thomas M.; Zhang, Huai-Min. (2020): NOAA 0.25-degree Daily Optimum Interpolation Sea Surface Temperature (OISST), Version 2.1. AVHRR-only daily files. NOAA National Centers for Environmental Information. https://doi.org/10.25921/RE9P-PT57. Accessed {date_accessed}.

Files

The newest day's final AVHRR-only OISST grid (sst, anom, err, ice; 0.25°), found through discover; one file per day from 19810901 (see header comment).
Downloaded by hand (no stable direct link).
The newest day's preliminary grid, same layout, found through discover (3 October 2026 on 2026-10-04); preliminary files are replaced by final ones about two weeks later.
Downloaded by hand (no stable direct link).

Status

Programme: Updated daily (the 3 October 2026 preliminary file was posted on 4 October). NCEI is moving its data to the cloud and warns of temporary access delays and degraded order services. NCEI is a NOAA line office exposed to the proposed FY2027 NOAA budget cut.
Updates: Daily, about one day behind (preliminary), final about two weeks later
Next release: 2026-10-05: Daily preliminary file for 4 October 2026.
Last check: Unchanged since the last fetch (2026-10-05T11:04:29Z)
Independent sources measuring the same thing: HadSST.4 sea-surface temperature anomalies C3S Climate Pulse daily global temperatures (ERA5)