I agree with @longgone about fog. Heavy fog. I also find thunderstorms romantic. Or really warm summer nights, with crickets chirping all around, on a big old porch. And falling snow, when everything is so calm and quiet. Crisp autumn days, too, with all of the trees alight, with a crackling fire going.
… I think I’m just romantic? I’m about to name all of the seasons and weather conditions. :D