NCEI Climate Data Online (CDO) v2 API
The legacy Climate Data Online v2 REST API exposes datasets, datatypes, stations, locations, data categories, and observation records. Requires a free token from ncei.noaa.gov/cdo-web/token in the `token` header. Enforces 5 requests/second and 10,000 requests/day per token. Being superseded by the Access Data Service v1, but still widely deployed.