Mostly Mauna Kea or Haleakala. Altitudes well in excess of 6,000 feet.
When the snow's "good", getting a ticket on Aloha or Hawaiian Airlines is like trying to fly to Vail at Christmas. Every year someone suffers from altitude sickness (hypoxia), or combines beers with "sleds" (boogie boards), or slides off the snowbank into a razor-sharp lava field. Kind of ironic considering that the ancient Hawaiians actually used to sled across lava fields and several are trying to revive the art of crafting holua (http://starbulletin.com/2002/05/26/travel/story1.html
And then there's the Mauna Kea Snowboard Championships. http://starbulletin.com/2001/12/18/news/story6.html
Our Hawaii-raised kid gets so maudlin about snow that we threaten to drive up there and kick her out of the car into the drifts. Maybe some day she'll get to experience an East-Coast winter-- without us!