Season
There are four seasons (Spring, Summer, Fall, Winter) each lasting seven in game days each. The frequency weather events, the types of weather, foliage color, etc. Vary per season.
Spring
In spring cherry trees bloom producing cherries.
Summer
Weather events like rain and thunder are more common during summer.
Fall
Leaf piles slowly form on the ground under tree leaves.
Winter
It can snow and ice will form in most biomes.