Top 3 European Mainland countries with worst climates

1) Growing Degree Days (GDD) is one of the important factors for planth growth; it is a measure of how much warmth there are for growth. However, it does not very well take into account the possibility of large deviation from normal and killing freezes. But the plants have to take that in account, indeed plants are extremely good at adapting to the local climate over time. In some inland areas, the theoretical GDD can not be used in spring or fall due to killing freezes. The high seems to be more important than the low for GDD, as the low is clipped and set to the base in the equation if lower than the base. The baseline is often 10C (like here) but can also be lower, such as 5C or 8C, depending on which plant it is and the possibilites in the local climate. For cool oceanic climates a lower baseline is often used, as the deviation from normal is much smaller than in inland climates so a lower baseline can be used by plants as the risk of killing freees is low. In inland areas, this is a bad idea as plants will not grow at that temperature in spring or have stopped growing in autumn due to the risk of killing freezes, which plants must adapt to. So in oceanic climates, plants can use lower temps due to less risk of killing freeze and thus more of the year for growth. In Norway, scientist usually use 5C baseline. But it can vary according to which plant species even here.

2) For this particular example, I have looked for normals for Ski, and the only one in the database is from a station 130 m ASL, but only for mean (no avg high/low). My guess is that Ski here is used for Ås, where the university for biological sciences is located, only 7 km away (Ski is the closest town to Ås). The weather station there is 92 m ASL, and there only exist normals for 1961-90 - Norway's met office is one of the few which still only use those, there are no official 1981-2010 normals. As 1961-90 was very cold here compared to both earlier and later years, it seems our met office work hard to make us look extra cold. The large difference from Ski/Ås to Voru in that chart seems strange, as Voru's summers are pretty similar to Oslo and Drammen. Drammen even has warmer June and Sep than Voru according to this page - which should be impossible looking at your chart.

Voru: www.infoclimat.fr/climatologie/normales-records/1981-2010/voru/valeurs/26249.html

Drammen: www.infoclimat.fr/climatologie/normales-records/1981-2010/drammen-berskog/valeurs/01480.html

So what climate normals are used? Is it 61-90 for all stations?

Further, the Ås/Ski weather station at that university has pretty cool highs for it's location in the SE lowland. For instance, June high (61-90) is only 19.8C at Ås while it is 21.2C on the warmest stations in the SE; such as Gvarv, and July only 20.8C compared to 22.2C for Gvarv. 1981-2010 would be ca 1C warmer.