3
$\begingroup$

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)

$\endgroup$

2 Answers 2

6
$\begingroup$

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

(summarized at NJWeatherScan, initially from manuals like this one (PDF page 66, page label 58):

Light rain: falling rate of less than 2.54 mm/h. This would be < 0.042 mm/min.

Moderate rain: falling rate of more than 2.8 mm/h, but less than 7.6 mm/h. This would be 0.042 mm/min - 0.127 mm/min.

Heavy rain: falling rate of more than 7.6 mm/h. This would be > 0.127 mm/min.

So clearly different standards compared to the DWD answer (note: 1 l/m² is equivalent to 1mm). Nowadays, automated weather stations use rain gauges with sensors, so a modern station with the computer inside has a clear and accurate computation of rain/snow falling rates. But there is no universal standards.

$\endgroup$
1
  • 1
    $\begingroup$ Since you reference the other answer, you should point out that DWD's use of l/m^2 corresponds to 1mm in NOAA's definition. $\endgroup$
    – Spencer
    Dec 10, 2021 at 16:29
4
$\begingroup$

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.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.