From Creatures Wikia
Seasons occur in nearly all the Creatures games, excluding the first (although seasons can be seen in Terra Nornia.) There are typically four seasons in a whole year: Spring, Summer, Autumn (Fall) and Winter.
Seasons were first introduced in Creatures 2, each season lasting a total of two hours. During Summertime, Albia begins to come to life, with caterpillars metamorphosing into butterflies and warm weather. During Winter, however, it can get extremely cold, which can cause the sea to freeze over. Many plants and animals will also become dormant during this season.
Seasons still occur in C3/DS, but more subtly. Although many metarooms can take advantage of the season system, the only effect it has on a standard world is a seasonal gender bias, with more chance of females during spring and more chance of males during autumn. The GAME variable engine_LengthOfSeasonInDays sets the season length, by default there are four days in a season.
Seasons affect the Creatures Village world on a much larger scale; snow will actually fall and settle on the ground during winter, and different fruit will grow depending on the season. It is worth noting that the playground area will remain the same, regardless of the season.