This page on the website of the KNMI reads archive copy at the Wayback Machine (in Dutch):

"Ik wil informatie van de KNMI-site op mijn eigen site gebruiken, mag dat?"
"Alle informatie die het KNMI op internet publiceert is openbaar en mag in principe door derden worden gebruikt, mits het KNMI als bron wordt vermeld. Onder deze voorwaarde staat het u vrij informatie te kopiëren van onze internetsite of links te leggen naar specifieke pagina's op onze site." [...]

Translated in English:

I want to use information from the KNMI-site on my own site. Is that possible?
All information published by the KNMI on internet is public and may in principle be used by third parties, provided that the KNMI is mentioned as a source. Under these conditions you are free to copy information from our internet site or to make links to specific pages on our site. [...]

Because they want to be mentioned as a source I have placed this under the following license:

This file is licensed under the Creative Commons Attribution-Share Alike 2.5 Netherlands license.

Fiel jo frij:

• te dielen – it wurk te kopiearjen, fersprieden en út te stjoeren
• te fermingen – it wurk oan te passen

Under de neikommende betingsten:

• Nammefermelding – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• Lyk diele – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

https://creativecommons.org/licenses/by-sa/2.5/nl/deed.enCC BY-SA 2.5 nlCreative Commons Attribution-Share Alike 2.5 nltruetrue