The climate of Puerto Rico in the Köppen climate classification is tropical rainforest. Temperatures are warm to hot year round, averaging near 85 °F (29 °C) in lower elevations and 70 °F (21 °C) in the mountains. Easterly trade winds pass across the island year round. Puerto Rico has a rainy season which stretches from April into November. The mountains of the Cordillera Central are the main cause of the variations in the temperature and rainfall that occur over very short distances. The mountains can also cause wide variation in local wind speed and direction due to their sheltering and channeling effects adding to the climatic variation.