I totally had a revelation in the Tsunami thread, so I have to post it here too. It fits in with the discussion about the rain.
Or maybe, if they are caught in between a time and/or space, they need to control the weather because the natural weather doesn't affect them. That's why they know its gonna rain! They have it on a timer like a sprinkler system to keep the island vegetation flourishing!
(Puff, Ashley, PL, TISCS, and I were discussing how real life weather may or may not affect the island if it is between a time or space.)