While at the top of Haleakala, see if Mauna Kea is peaking through the clouds.
In the center of this photo is Mauna Kea all the way over on the Big Island. It stands almost 3,800 feet higher than Haleakala and its peak is about 80 miles from this vantage point. But because of the Earth's curvature and the distance, it almost looks even.
Be sure to check out my Big Island page for pictures looking back at Haleakala from the top of Mauna Kea.
Haleakala Crater Road -- one of the fastest-ascending roads in the world. This grand corniche has at least 33 switchbacks; passes through numerous climate zones; goes under, in, and out of clouds; takes you past rare silversword plants and endangered Hawaiian geese sailing through the clear, thin air; and offers a view that extends for more than 100 miles. Going to the summit takes about 2 hours from Kahului.
As you go up the slopes the temperate drops about 3°F every 1,000 feet, so the temperature at the top can be 30°F cooler than it was at sea level. Come prepared with sweaters, jackets, and rain gear.