{"id":"station-rainfall-totals","slug":"station-rainfall-totals","name":"Station Rainfall Totals Dataset","description":"Annual and seasonal rainfall totals calculated from the daily records of 146 long-running stations across eleven countries, the earliest beginning in 1827, together with each station’s own thirty-year reference average. A daily record answers what fell on a given day; these are the figures that answer whether a year was wet.","methodology":"Each total is the sum of the daily readings the station holds for the period, and is produced only where the period is nearly completely covered. A month qualifies when it is missing no more than five days and no more than three of those fall consecutively — two tests rather than one, because five scattered absences and a five-day outage are the same number and not the same problem, and rain arrives in runs. A year or a season qualifies only when every one of its months does. Where the test fails nothing is produced: an absent day is never treated as a dry one, and no partial period is scaled up to a whole. Every total records how many days it was added from, and where any day is missing it states that the true figure can only be higher. Winter runs from December through February and is named for the December, so a single winter stays in one value. The thirty-year average is the mean of a station’s own annual totals across the complete WMO 1991–2020 period, produced only where all thirty years qualify — which is why most stations have none.","domains":["precipitation"],"metricIds":["precipitation-annual","precipitation-seasonal"],"subjectScope":"The GHCN-Daily stations Hydrionis holds a daily rainfall record for, together with the UK areal series that carry a calculated reference average","cadence":"irregular","version":"1.0.0","released":"2026-08-31","derived":true,"changelog":[{"version":"1.0.0","date":"2026-08-31","summary":"First release: annual and seasonal totals from the daily station records.","methodVersion":"total-over-period 1.0.0","additions":["Annual rainfall totals for every station-year densely enough covered to be added up, the earliest from 1827.","Seasonal totals on the meteorological convention, with winter carried across the new year rather than split at it.","A thirty-year reference average for each station whose 1991–2020 record is complete."]}],"limitations":["A total is a sum of days, so it is only as complete as the record beneath it. Where days are missing the total is stated as a lower bound and the number of days held is recorded on the value — it is never adjusted upwards to compensate.","These are point measurements added up. A station total is not an area or catchment rainfall figure, and averaging whichever stations exist does not make one.","Rain gauges under-catch in wind and snow, most severely at exposed and upland sites, so a long station record can trend for reasons of site and instrument rather than climate. A total inherits that entirely.","A reference average describes the thirty years it was computed over. An anomaly against a 1991–2020 baseline is not comparable with one against 1961–1990, and in a warming climate the difference is systematic rather than random.","Nothing here is a national or regional rainfall statistic, and no total is comparable with a publisher’s own gridded product, which is built from many more gauges and corrected for exposure."],"context":{"hydrionisClass":"water-driver","whyHeld":"Rainfall is what makes rivers do what they do, and it is not itself a measurement of water in a river. These are the totals that let a station’s two centuries of daily readings be set beside a flow record, a groundwater level or a drought — the arriving side of the system rather than the water already in it. A wet year at a gauge is a statement about that gauge and its exposure, never about the catchment around it.","waterRelevance":["River flow and the shape of a hydrograph","Groundwater recharge and the water table’s seasonal cycle","Reservoir inflow","Drought onset, depth and recovery","The baseline a rainfall anomaly is measured against"],"suitableUses":["How wet or dry one station’s year or season was against its own long record","Anomalies and percentiles at a station, against the stated 1991–2020 reference period","Setting rainfall beside a nearby flow or groundwater record on a shared time axis, with the distance between them stated","Long-run rainfall change at a single station, where the record is genuinely continuous and its gaps are read alongside it"],"unsuitableUses":["Area or catchment rainfall — that needs a gridded product built from many gauges and corrected for exposure, not a total from the one gauge that happens to be there","Comparing one station’s total with another’s as a statement about which place is wetter, when the difference may be exposure, gauge type or observation-day convention","Attributing a flood or a low flow to a particular season’s rainfall without catchment evidence Hydrionis does not hold","Any use in which a year Hydrionis withheld is read as a dry year rather than as an unread one"],"joinDimensions":[{"kind":"measured-proximity","on":"The great-circle distance from the station to the nearest Hydrionis measurement point, stated per station and never more than 30 km","limitation":"Proximity is not catchment membership. A station 3 km from a gauge may sit outside its catchment entirely, and the rain measured there may never reach that gauge."},{"kind":"time-only","on":"Shared annual and seasonal periods with any other Hydrionis series","limitation":"A shared time axis supports showing two series together and nothing more. Two records covering the same years are not thereby related, and a wet year beside a high flow year is a coincidence until a catchment says otherwise."}],"relationshipConfidence":"proximate","eligibility":{"api":true,"download":true,"overlay":true,"publicPage":false}},"observationCount":85722,"seriesCount":379,"subjectCount":163,"from":1827,"to":2026,"sourceIds":["noaa-ghcn-daily","uk-metoffice-haduk"],"units":["mm"],"redistributable":true,"commerciallyReusable":true,"citation":"Hydrionis (2026), Station Rainfall Totals Dataset, version 1.0.0. Retrieved from https://hydrionis.com/data/datasets/station-rainfall-totals/","downloads":[{"file":"/downloads/observations-precipitation-noaa-ghcn-daily.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 1 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part2.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 2 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part3.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 3 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part4.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 4 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part5.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 5 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part6.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 6 of 7 (1,000,000 rows)"},{"file":"/downloads/observations-precipitation-noaa-ghcn-daily-part7.csv","format":"CSV","label":"precipitation observations from NOAA NCEI, part 7 of 7 (683,264 rows)"},{"file":"/downloads/observations-precipitation-uk-metoffice-haduk.csv","format":"CSV","label":"precipitation observations from Met Office (55,369 rows)"}],"apiPath":"/api/v1/datasets/station-rainfall-totals.json","fields":[{"id":"precipitation-annual","name":"Annual precipitation","definition":"Total depth of precipitation falling over a defined area in a calendar or water year.","unit":"mm","nativeGeography":["monitoring-station","grid-cell"],"comparabilityNotes":"Annual totals for different countries are not comparable as a measure of water availability. A large arid country and a small wet one can have similar national average rainfall while having entirely different renewable water resources per person. Gauge networks also differ in density, and mountain precipitation is systematically under-measured."},{"id":"precipitation-seasonal","name":"Seasonal precipitation","definition":"Total depth of precipitation falling over a defined area within a meteorological season.","unit":"mm","nativeGeography":["monitoring-station","grid-cell"],"comparabilityNotes":"Meteorological seasons are fixed three-month blocks — winter is December to February, and its December belongs to the previous calendar year. Comparing a season across years is valid; comparing adjacent seasons is not."}]}