Once Tashi Met a Dragon by Anna Fienberg

No one had ever seen the dragon, but once a year it would send smoke and thunder down the mountain, and soon the rains would follow. Now the skies were always blue, the creeks were drying up and the people were hungry. What was happening up there? When Tashi reaches the dragon's golden palace, he meets an angry young dragon who is upset because his mother is under the spell of a demon sleep and he can't wake her up.