Try and google around, you never know what you may find.
Found the site below, not sure how helpful it will be:
http://www.yr.no/place/K...r_by_hour_detailed.html
http://www.yr.no/place/K...lley/Naivasha/long.html
If they have the data that you need, to get historical data, you'll need to contact them.
To contact them, you will need to translate their contact page to English by using a service like
http://translate.google.com/
Contact page url:
http://om.yr.no/sporsmal/kontakt-yr-no/
Note that once you use google translate, the Captcha will be disabled, so you will need to open another tab with the original, untranslated contact page that has captcha enabled, fill it, using the translated version as a guide.
They tried to bury us, they didn't know we were seeds.