The landforms of the Hawaiian Islands allow for a variety of weather conditions and biological ecosystems. There are places in the islands that only average 10 inches of rain per year, whereas Mt. Waialeale on Kauai is considered one of the wettest places on the planet, receiving well over 400 inches. With prevailing winds coming from the east, moisture-laden clouds rise when they hit the islands' mountains. Subsequently, they deposit a lot of rain on the eastern slopes. Consequently, the leeward/western sides of the islands are much drier than the windward/eastern ones.

As mentioned in Chapter 1, even though there isn't a lot of seasonal variation to be found in Hawaii, it's still possible to recognize the seasons of summer and winter. Summer extends from May through October, and the winter months are November through April. Winter brings a bit more moisture and the temperature drops about 5 degrees at sea level. Keep in mind, though, that temperatures tend to lower with elevation gain by about 3 degrees per 1,000 feet. This can be a great strategy to beat the heat, but it can also lead to some chilly surprises. If it's a lovely 80 degrees at the beach in Kona, it might be 40 degrees on the summit of Mauna Kea, and even colder if the wind is blowing.

Clear Skies!

Speaking of Mauna Kea, Hawaii's biggest mountain is home to an impressive complex of astronomical observatories. Over thirteen can be found on its summit, and astronomers from all over the world take turns using these various facilities up where the air is clear and the view seemingly unobstructed. Other observatories can be found on Mauna Loa and Haleakala, making Hawaii a center for scientific research.