Rain

Rain is a transition event that can occur in any surface biome (except for the Snow Biome, where it manifests as a blizzard). When rain begins to fall, the music changes and the lighting and background dims. It doesn't make water levels rise, but it does enable new and variant enemies to spawn. It's unconfirmed whether the rain event happens randomly or has a predictable pattern. It can happen during both day and night, and daylight/moonlight is reduced.

During the rain, Zombies will convert to Rain Coat Zombies. If a Snow Biome is nearby, then it's possible for Eskimo Zombies to spawn as well. Rain and Blizzards can overlap in the same area, causing monsters from both biomes to spawn in the same area. Snowfall increases in this case, leading to a blizzard.

During the rain, Goldfish are capable of moving on land and "walking" on their fins. Also, NPCs will stay inside their homes during the rain, just like during the night.