As part of the home dashboard I am developing, I get information about incoming rain. It is given in mm/min.

Is there a consensus on the precipitation rate that is called "light rain", or "heavy rain"? (I would like, if this is possible, to use some standardized naming)


If there was a worldwide standard, then WMO would have imposed it to its members. Here are the definitions in the American (NOOA/NWS) standard:


Light rain: falling rate of less than 2,54 mm/h.

Moderate rain: falling rate of more than 2,8 mm/h, but less than 7.6 mm/h.

Heavy rain: fallin rate of more than 7.6 mm/h.

So clearly different standards compared to DWD. Nowadays, automated weather stations use rain gauges with sensors, so one by means of the computer inside the station has a clear and accurate computation of rain/snow falling rates.


The German Weather Service (Deutscher Wetterdienst, DWD) provides the following definitions:

Heavy rain is defined as large amounts of precipitation during a fixed period of time. [...]

The DWD issues warnings of heavy rain using three categories:

  • heavy rain: 15 to 25 l/m² within 1 hour or 20 to 35 l/m² within 6 hours
  • severly heavy rain: 25 to 40 l/m² within 1 hour or 35 to 60 l/m² within 6 hour
  • extremely heavy rain: above 40 l/m² within 1 hour or above 60 l/m² within 6 hour

Source: https://www.dwd.de/DE/service/lexikon/begriffe/S/Starkregen.html and https://www.dwd.de/DE/wetter/warnungen_aktuell/kriterien/warnkriterien.html?nn=508722#doc453962bodyText3, translation my own.

Heavy rain is distinct from constant rain by the period of time, over which the rain falls, as well as the total amount of rain per m². Still, heavy rain events may be part of constant rain periods.


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