Dominica has a tropical rainforest climate and some areas bordering on a tropical monsoon climate with characteristically warm temperatures and heavy rainfall. Excessive heat and humidity are tempered somewhat by a steady flow of the northeast trade winds, which periodically develop into hurricanes during the Northern Hemisphere's summer. The steep interior slopes also alter temperatures and winds. Because of the moderating effects of the surrounding ocean temperature ranges are slight. Average daytime temperatures generally vary from in January to in June. Diurnal ranges are usually no greater than in most places, but temperatures dipping to on the highest peaks are not uncommon.