I have visited Haleakala two times now. The road takes you all the way to the summit at a little over 10,000 ft. It is a beautiful winding drive to the summit. You are driving through green pastures and green vegetation, but as you climb higher and higher, the landscape becomes more barren.
Windward slopes of Haleakala are covered by rain forest with a yearly rainfall of 120 to 400 inches. Leeward slopes are covered by dry forest with 20 to 60 inches of yearly rainfall.
What was impressive to me, especially on my first trip was, that as we climbed higher we left the clouds beneath us. Beautiful white clouds below, clear blue sky above, and the mostly brown mountain around you.
There was something special about it.
The weather on the summit can change very quickly. It can be very hot one minute and turn cold the next. Both times when I was there it was cold. It is a good idea to take a warm jacket, otherwise your whole experience might be lost.
The large basin on the top of the mountain was not created by volcanic activity, but by wind, water and possibly glaciers.
Many people ride bicycles down the Haleakala mountain. It must be a thrilling ride. Usually these are organized trips, and when driving it is important to watch for cyclists since the road is relatively narrow.