The first picture I put in summer and the second winter, I saw almost no difference
But that's the point: the scenery doesn't look like that. Spring/Summer are green, your screenshots looks more like Winter and Fall, looking at the surrounding landclass.
in winter there is snow at the airport even when it is not snowing.
That's exactly the opposite of what you winter screenshot (the first one, the one you are assumed summer), which correctly shows no snow, because it's not snowing. Snow, in fact, will appear ONLY when snowing.