Pokémon Season 4 Episode 28

On the dry and dusty road to Olivine City, our heroes notice beautiful lights shining in the sky ahead of them. Realizing they are coming from just above the dried up lake on Remoraid Mountain, they run to the Remoraidian Ruins. Although the surrounding area is utterly arid, our heroes take note of the plentiful plant-life. What could be causing this change in climate? Does it have something to do with the lights above the bone-dry basin?