Why do the leaves on trees seem to turn upside down before a storm?
Before a cold front arrives with its clouds and rains, the wind is often from the southwest. With the wind in this direction, the plant or tree orients itself to get optimum sunlight, and the leaves are in an unstable position with respect to the wind moving past them. This instability makes the leaves flip over. The unstable leaves then foretell the approach of a cold front which is likely to bring rain.