NOAA Open Data Dissemination (NODD)
NOAA Open Data Dissemination (NODD) puts the US National Oceanic and Atmospheric Administration's vast archive on the major cloud platforms, Amazon Web Services, Google Cloud, and Microsoft Azure, so you can read it next to where your compute already runs. The programme spans weather-model output (such as the GFS and HRRR forecasts), radar (NEXRAD), satellite imagery (GOES), long-run climate data records, ocean data, and surface station observations, all told one of the largest environmental archives in the world.
Access is genuinely open: the data lives in public cloud buckets you can list and pull without an account, and there is no egress charge when you read it from within the same cloud, which matters because the volumes are enormous. Most of it arrives in scientific gridded formats, NetCDF, GRIB2, and increasingly Zarr, that hold numbers rather than prose. For station-level records, NOAA's Climate Data Online service and its API return weather and climate observations plus station metadata as JSON or CSV, which is far friendlier to a text pipeline.
The honest truth for RAG is that NODD is mostly numeric, not textual, so it is best when your system needs to reason over station catalogues, dataset documentation, and metadata, or when you are pairing a language model with retrieved numeric context that you convert into short natural-language summaries ("On 3 July, station X recorded 28 mm of rain"). A climate or weather assistant grounded in station histories and product descriptions is the natural fit; a pure text-retrieval project will find less here than the scale suggests.
On licence there is nothing to worry about: as US Government work it is public domain, so commercial use, redistribution, and derivatives are all unrestricted, with no attribution required (though crediting NOAA is polite). Watch the sheer size and the format learning curve instead. For European coverage and reanalysis products, Copernicus and its ERA5 climate dataset are the natural companions alongside NOAA.
Related sources
Copernicus (EU Earth Observation)
The EU's flagship Earth observation programme. The Copernicus Climate Change Service portal provides authoritative information about past, present, and future global climate, derived from Sentinel reference products alongside other satellite observations and in-situ measurements.
Met Office DataPoint / CEDA
The Centre for Environmental Data Analysis hosts UK atmospheric and Earth observation data, including Met Office archives, climate model outputs, and satellite data.
NASA Earthdata
The home for full and open access to NASA's Earth science data collections. The umbrella portal for the largest collection of freely available Earth science data in the world, with over 12,400 datasets spanning land, ocean, atmosphere, and cryosphere, collected by satellite missions, airborne campaigns, and ground stations.
WeatherBench 2
Google Research's open benchmark and curated ERA5-derived data archive for evaluating data-driven global weather models over the one-to-fifteen-day range. It bundles an Apache-licensed evaluation framework, cloud-hosted ground-truth and baseline forecast datasets in Zarr, and a continuously updated leaderboard ranking models such as GraphCast and Pangu-Weather against ECMWF's IFS.