This must have been mentioned before, but just in case it hasn’t… how about a summer and winter global season affecting all biomes that cycle every 20-30 game days with a 2-3 day transitional state (spring, autumn). So say in winter, its darker for longer, say 2/3 of the time and snowy everywhere - but warmer and less snow in the desert, outrageously cold in the north, the temperate zone somewhere… well temperate in the middle! Summer, vice versa?
I’m just reminded of “Don’t Starve” where the season thing really worked well. You HAD to plan for the winter in particular, with fuel and food stores. Your crops failed and there was nothing to hunt