The oceanic climate of the Faroe Islands is mild.  Temperature changes are relatively small.  Fog and precipitation are typical weather conditions.  The average precipitation is about 1500 mm.  The North Atlantic Current keeps the harbours ice free during winter.  The natural flora of the islands is mainly based on mosses and bog vegetation.  Woods thrive badly, because of the strong westerly winds.  Hardy tree species have been planted in suitable and sheltered places.  Frogs, snakes and wild mammals were nonexistent, when the islands were settled.  Hares, rats and mice were brought to the islands by the arriving vessels.  The avifauna is more lively, especially the seafowl, i.e. puffins and eider ducks, which are exploited.