Island weather is unsally pretty consistent. The average daytime summer temperature at sea level is 85 while the average daytime winter temperature is 78! At night, there is only a 10 degree drop in temperature. Hawaiian weather patterns are affected by high pressure zones that bring cool, moist trade winds down onto the island's northeastern slopes. These winds are forced up-slope by the mountain heights where their moisture condenses into clouds that produce rain. Most of the rain falls in the mountains and valleys on the windward (northeastern) side of the islands. It is this weather phenomenon that creates Hawaii’s rich, green, tropical environment. SURFING in Hawaii is good depending on wave action during different parts of the season, but you can expect the water temperature to be 74 or higher!