Data source

This dataset provides a daily time series of precipitation for Massachusetts, expressed as the average precipitation (inches) across all MA GHCN/COOP stations that reported on each day. Storing daily values allows downstream analysis to apply any aggregation or threshold — annual totals, heavy-rain-day counts (e.g. days ≥ 1 inch), or event-level correlations with CSO discharges — without re-fetching data.

Precipitation observations come from the NOAA Applied Climate Information System (ACIS), which aggregates data from the GHCN and COOP station networks operated by the National Weather Service and state climate offices. No API key is required for ACIS access. Data are fetched year-by-year in daily resolution and averaged across reporting stations.

Note that the number of reporting stations has increased over time as the COOP network expanded; the n_stations column reflects the count of stations contributing to each day’s average. All values represent a simple (unweighted) spatial average and are intended as a qualitative index rather than a spatially precise estimate.

This dataset is updated 3 April 2026.

The script used to generate this data is get_data/get_MA_precipitation.py.

Download archive

• MA daily precipitation CSV format

Data table

Date	Avg Precipitation (inches)	Number of Stations
2000-01-01	0.0	83
2000-01-02	0.02	80
2000-01-03	0.12	73
2000-01-04	0.34	87
2000-01-05	0.57	82
2000-01-06	0.0	79
2000-01-07	0.0	70
2000-01-08	0.0	76
2000-01-09	0.0	68
2000-01-10	0.42	74

Table shows a sample of rows from the full dataset.