In 2021 the Dutch Meteorlogical Institute (which has the predicate royal, koninklijk in Dutch, hence KNMI) started using new normal values. Something they do every 10 years shifting the normal to the most recent three decades.
So from the first of january the normal values are calculated from the years 1990 until 2020 (included). However, the KNMI only publishes the normal values for their official numbers i.e. De Bilt where their office and main weather station is.
So how do I follow? How do I get my normal values for Wagenborgen which is some 175 km north east of De Bilt as the crow flies. The nearest official KNMI stations are Nieuw Beerta and the Airport Eelde. Usually I use Nieuw Beerta for my temperature and humidity calibrations but unfortunately, Nieuw Beerta does not measure rain.
As Airport Eelde is more land inwards, the temperature will likely deviate from Nieuw Beerta so I made the choice to create the normal temperatures from Nieuw Beerta and the normal rain values from Eelde.
I took the values from the daily KNMI measurements page: rain for Eelde and Temperature for Nieuw Beerta. Then I wrote a short program to read the output and calculate the resulting normal values for monthly temperatures and monthly rain. The resulting values I filled in in the CumulusMX settings for the NOAA reports from where they are fetched to be used in the CumulusUtils reporting style you see on the website.
The new normal values used for my Wagenborgen weather station for the period of 1990 – 2020 are shown in the following table:
January:
February:
March:
April:
May:
June:
July:
August:
September:
October:
November:
December:
Temperature
2,5
2,8
5,3
8,9
12,4
15,2
17,5
17,5
14,4
10,2
6,2
3,3
Rain
72.7
54.7
54.1
41.3
57.9
65.0
85.0
77.8
75.4
71.4
70.0
79.4