The effects of trade winds on Hawaii weather present in the varied amounts of rain in the windward and leeward sides of the islands, as well as the mildly warm temperatures throughout the island group. In Hawaii, trade winds prevail 80 to 95 percent of the time in the months from May to September and 50 to 80 percent during the rest of the year. They cause showers in the windward sides and create warm temperatures all year.
The trade winds that blow through Hawaii islands comes from the North and South America to Asia. They meet Hawaii's high mountains which results in precipitation on the north and northeast sides of the islands, the windward side. Showers are common in those areas, but the majority are light and brief. Heavy rains are rare, and mostly without thunder and lightening. In the leeward lowlands, dry weather is prevalent except for occasional light showers which drift over from the mountains to windward. Because of the persistent trade-wind flow throughout the year, the islands don't have a defined "rainy season."
The trade winds also provide a system of natural ventilation for the islands: they bring warm air, which has moved great distances across the tropical seas, and create the mildly warm temperatures.