Precipitation
Precipitation
To determine whether the precipitation criterion for bad weather is met (as per BSCHeG), both the observation period and the intensity of precipitation must be examined in detail.
In general, a distinction must be made between
- precipitation before normal working hours (5 p.m. to 7 a.m.) and
- precipitation during normal working hours (7 a.m. to 5 p.m.).
Precipitation includes snow, hail and all forms of rain.
Precipitation - before normal working hours
If large amounts of precipitation fall before the start of working hours, it can cause a bad weather condition for the following day or for the subsequent working hours on the same calendar day.
Precipitation that falls shortly before the start of working hours is evaluated as having the greatest influence on work activities, since it has the least time to run off and/or dry up.
The observation period begins at 5 p.m. on the preceding day and ends at 7 a.m. on the day in question.
The following table shows in detail how bad weather hours arise as a function of duration and intensity of precipitation:
| Indicated minimum amount of precipitation leads to | |||
| Observation period | 1 hour bad weather | 2 hours bad weather |
3 hours bad weather or rest of day |
| 6:00 - 07:00 | 1,0 mm | 1,7 mm | 2,4 mm |
| 5:00 - 07:00 | 1,7 mm | 2,4 mm | 3,0 mm |
| 4:00 - 07:00 | 2,4 mm | 3,0 mm | 3,5 mm |
| 3:00 - 07:00 | 3,0 mm | 3,5 mm | 4,0 mm |
| 2:00 - 07:00 | 3,5 mm | 4,0 mm | 4,5 mm |
| 1:00 - 07:00 | 4,0 mm | 4,5 mm | 5,0 mm |
| 24:00 - 07:00 | 4,5 mm | 5,0 mm | 5,5 mm |
| 23:00 - 07:00 | 5,0 mm | 5,5 mm | 6,0 mm |
| 22:00 - 07:00 | 5,5 mm | 6,0 mm | 6,5 mm |
| 21:00 - 07:00 | 6,0 mm | 6,5 mm | 7,0 mm |
| 20:00 - 07:00 | 6,5 mm | 7,0 mm | 7,5 mm |
| 19:00 - 07:00 | 7,0 mm | 7,5 mm | 8,0 mm |
| 18:00 - 07:00 | 7,5 mm | 8,0 mm | 8,5 mm |
| 17:00 - 07:00 | 8,0 mm | 8,5 mm | 9,0 mm |
For example, if at least 9.0 mm of precipitation falls in the entire observation period (5 p.m. to 7 a.m.), the rest of the work day (the following day) counts as bad weather.
Precipitation - during normal working hours
Intensity of precipitation
Precipitation volumes: each 1.0 mm (1 litre per square metre) per hour during normal working hours results in one hour of bad weather. Such precipitation volumes are caused either by ongoing rain or by brief heavy showers, but never by dripping or drizzling rain
Duration of precipitation
If the precipitation lasts for at least 30 minutes per hour, the relevant hours are also counted as bad weather hours regardless of the amount of precipitation.
(Note: This applies to “dripping” rain, which can also reach about 0.7 to 0.8 mm of precipitation in 30 minutes. It does not apply to drizzling rain, which does not trigger the detector.)
Analysis of precipitation is on an hour-by-hour basis.
The results of a precipitation event can sometimes even lead to multiple hours of bad weather. For this reason, the observation period is assessed over a one-hour, a two-hour, and a three-hour period.
Depending on how much it rains or snows in the given observation period, the result may be that just one hour, two hours, or the rest of the day is deemed bad weather.
| Indicated minimum amount of precipitation leads to | |||
| Observation period | 1 hour bad weather | 2 hours bad weather |
3 hours bad weather or rest of day |
| 1 hour | 1,0 mm | 1,9 mm | 2,7 mm |
| 2 hours | 1,9 mm | 2,7 mm | 3,4 mm |
| 3 hours | 2,7 mm | 3,4 mm | 4,0 mm |
If there is 2.7 mm of precipitation in one hour, the rest of the work day is deemed bad weather; e.g. in case of 2.7 mm of precipitation in three hours, the result is one hour of bad weather.