How about this: Sky and sea are very often linked in myth.

The water cycle is caused by the Sky people who are ex-citizens of the Sea. They liked water, but didn't like the Sea, too much confinement. So they left in search of open space, but they also didn't like Earth which required them to walk when they were used to swimming and drifting, so they kept going upward. In the air they could fly.

But the Sky people were cursed as a result of leaving. The Sea people coloured the sky blue to remind them of what they had left behind, but they can never hold on to water. The Sky try to take water from the earth and the air, and hoard it as clouds, but they can never hold onto it forever and it has to fall back to earth and the sea, and the clouds always disappear.