Precipitation: methodology
Provenance for the series on Precipitation. This page has its own URL so it can be cited alongside a figure.
- Source
- NOAA NCEI nClimDiv
- Dataset identifier
- noaa_precipitation
- Update cadence
- Monthly, ~1 week lag
- Unit
- inches
- Coverage
- 18 series · 1895-01-01 to 2026-09-01
- Vintage published here
- 2026-10-30
Total monthly precipitation in inches, from NOAA's nClimDiv dataset, as published and not recomputed here. The period of record begins in 1895.
These are not station readings. nClimDiv county values are area-weighted averages of grid-point estimates interpolated from station data on a nominal 5 km grid, built from the Global Historical Climatology Network (GHCN-Daily). A county figure is therefore an estimate of the county's average, not a measurement taken anywhere in particular. In a state with Nevada's topography the difference matters: a valley gauge and a range crest in the same county differ by more than the county average conveys.
Revisions. NOAA updates the most recent two calendar years every month, and restates the whole period of record when the underlying dataset changes version. We do not overwrite what was published before: each run stores its values under a new vintage, so a figure cited last month stays retrievable.
Months that have not happened yet. NOAA pads the current calendar year to twelve months using a sentinel value. We drop those months rather than storing them as nulls, so the series simply ends at the last month NOAA has computed.
Revisions and vintages
Every observation we store carries the date it was published, and a revision lands as a new vintage rather than overwriting the old one. The figures on this site are the most recent vintage, stamped above; a figure you cited earlier stays retrievable even after the source restates it.
The full series, including the flag and vintage of every value, is in the CSV.