The islands are well known for the environmental diversity that occurs on high mountains within a trade winds field. Most of Hawaii experiences only two seasons; the dry season runs from May to October and the wet season is from October to April. Windward sides face cloud cover. Because of the hotspot's location, all currently active land volcanoes are located on the southern half of Hawaii Island. This isolation , in combination with the diverse environment including extreme altitudes, tropical climates, and arid shorelines , allowed for the evolution of new endemic flora and fauna. The Hawaiian islands were formed by volcanic activity initiated at an undersea magma source called the Hawaii hotspot. Bush on June 15, Hawaii has more endangered species and has lost a higher percentage of its endemic species than any other U. Because the islands of Hawaii are distant from other land habitats, life is thought to have arrived there by wind, waves i. The process is continuing to build islands; the tectonic plate beneath much of the Pacific Ocean continually moves northwest and the hot spot remains stationary, slowly creating new volcanoes. The silver glow around the southwest of the islands is the result of calmer waters. The rainy climate impacts soil development, which largely determines ground permeability, affecting the distribution of streams and wetlands. On a single island, the climate around the coasts can range from dry tropical less than 20 inches or millimeters annual rainfall to wet tropical; on the slopes, environments range from tropical rainforest more than inches or 5, millimeters per year , through a temperate climate, to alpine conditions with a cold, dry climate. Hawaii is the only state to have never recorded sub-zero Fahrenheit temperatures.