W1 nailed the atmospheric environments in all departments, i remember having a sense of tension walking in streets of vizima at night, dark and wet i just wanted to go in a tavern, and wait for the day time
I didn't, I really enjoyed the night, but that is probably because in RL I'm also kind of a "Night-Person" if you know what I mean.
As for the question of the OP, I can only agree with what most people said here. Of COURSE there should be a big variety of moods and atmospheres in different places and different weather conditions. I mean, a sunny day in the swamp might have a more dark and gloomy atmosphere than a rainy day in one of the villages with wide open fields around.
It always depends on context. A swamp is dark and foggy, will probably only ever be a little bit brighter in the morning until noon, and only if it's a sunny day, which might not be there so often based on regions.
Skellige is probably mostly frosty and should "feel" cold and icy, barren and harsh.
Different moods create a contrast and diversity, variety, it makes up the palette of emotions you go through an determines how much you value each place in the world. It shows the world LIVES and has a lot of sides to it.
I loved the atmospheres in the Witcher 1. Hell, I even loved it in TW2, it was different but very well fitted the plot I thought.
They are on a good path with TW3 I think. If there is ANYTHING that they did right from the start and that I did never really see bad quality or concerning impressions/material of during all the trailers and advertising then it is the atmosphere.