I’m guessing the devs are already working on seasons for the game, but I have some ideas for them.
Farming
I think there should be a feature where there could be a range of crops that are season specific. Maybe corn can only be grown in summer and pumpkins in fall (for example). This suggestion relates to the system used in Stardew Valley (Parsnips in Summer, Pumpkins in fall, etc).
Appearance
This is quite an obvious one, but there should definitely be a change in the colour of the grass and the tree leaves. Maybe even the design of the ground can be changed so it is either floral or covered in leaves. During winter trees could have no leaves, the ground can be covered in snow and the lakes could be frozen.
Hearthling Mood and Traits
Your Hearthlings could get either cold or hot, so they need a different style of clothing (like the Winter Worker Outfit) This would change their mood, making them happy or upset. Hearthling Traits could give resistance to cold or warmth.
That’s all I have for now, thanks for reading and Happy New Year!