Dream pop and the relationship to weather and season is something I've heard many people in the community describe independently.
The clustering of certain dream pop records around autumn and winter listening is consistent enough across different people that I don't think it's purely subjective. There's something about the formal characteristics of dream pop — the cool timbres, the reverb-heavy production that creates a sense of space expanding in cold air, the specific quality of melancholy — that resonates with the phenomenology of late autumn.
I've thought about why this might be true. One theory is that dream pop shares formal characteristics with the acoustic environment of late autumn — the muffled sound of overcast days, the way low light changes the temporal quality of afternoons, the ambient sound of wind and bare branches. The music is in some sense already about the season it resonates with.
Another theory is simpler: the emotional register of late autumn and dream pop are similar, and we naturally match music to emotional context. We play melancholy music when we're in melancholy seasons because the resonance is productive rather than depressing.