Fetch historical observation records from a NOAA CDO dataset for a given date range. Requires datasetId (e.g., GHCND for daily, GSOM for monthly), startDate, and endDate. Optionally scope to specific stations, locations, and data types. Date range limits per request: sub-daily and daily datasets (GHCND, PRECIP_15, PRECIP_HLY, NORMAL_DLY, NORMAL_HLY) are limited to 1 year; monthly and annual datasets (GSOM, GSOY, NORMAL_MLY, NORMAL_ANN) are limited to 10 years. For climate normals (NORMAL_*), use startDate=2010-01-01 and endDate=2010-12-31 — that is the API proxy year regardless of which 30-year period is being described. Returns flat tuples of { date, datatype, station, value, attributes }. Strongly recommended: pass units=metric or units=standard — without it, GHCND values are raw tenths-of-unit integers (TMAX=256 = 25.6°C, PRCP=12 = 1.2mm). GSOM/GSOY are already scaled.
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