The weather rating is an objective evaluation of the weather. Sunshine, wind and rain determine the rating score. The rating score goes from 1 to 10. The weather rating gives us an all-year-round objective points score for the weather.
The Belgian Hugo Poppe came up with the idea of measuring the quality of the weather by giving it a mark out of ten«. Harry Geurts (KNMI) developed the Dutch version also giving marks out of ten. For several years the weatherman Jan Pelleboer, who died in 1992, used a similar system in his weather reports but in his case gave subjective scores.
The weather rating is solely based on the daytime weather. Night-time is not included. We start with a 10 and deduct points for: a lot of wind, cloud, precipitation and mist. A sunny, dry day with little wind gets a 10.
We work out the average cloud cover using the forecast between 7 a.m. and 7 p.m..
Deduct 0 if the average is equal to or smaller than 1/8.
Deduct 1 if the average is between 2/8 and 5/8.
Deduct 2 if the average is between 6/8 and 7/8.
Deduct 3 if the average is more than 7/8.
Fog and mist
We look at the daytime fog and mist forecast.
Deduct 0 if there is no mist forecast.
Deduct 1 if less than 3 hours of mist is forecast.
Deduct 2 when there is more than 3 hours of mist expected.
This is calculated in relation to the duration of expected rainfall.
Deduct 0 if less than 10 minutes of rain is forecast.
Deduct 1 for 10-90 minutes of rain
Deduct 2 for 90-300 minutes of rain
Deduct 3 for 300-500 minutes of rainfall
Deduct 4 for more than 500 minutes rainfall.
Here we look at the daytime maximum wind strength (average of 10 minutes).
Deduct 0 if this is 0-2 Bft..
Deduct 1 if this is 3 Bft..
Deduct 2 if this is 4 or 5 Bft..
Deduct 3 if this is 6 Bft. or more.
Theoretically it is possible to get a weather rating of less than 1. If this happens the rating is nevertheless kept as 1.
The temperature is not included in the weather rating.
This has been done on purpose, for two reasons:
The temperature is linked to the other elements that are used. Little wind, a lot of sunshine and no rain, almost always give a pleasant feel.
The temperature actually plays a limited role in the experiencing of weather quality. A cool day with little wind, a lot of sunshine and no rain is still highly valued by most people.