Precipitation is related to high and low preasure air, with low pressure systems lead to rain

Low-pressure systems as associated with higher chances of precipitation than high-pressure systems. This is because, in the low-pressure system, the local air above land is heated up by the sun and begins to rise. Cooler air masses from the surrounding blow towards the region to replace the rising air and pushes the warmer air up into the atmosphere. As the warm air rises it cools and condenses to clouds that later precipitate.  

In higher pressure systems, cooler denser air masses fall from the atmosphere to the land surface. As they fall, the pressure on the local grounds increases hence warming up the descending air. This air also pushes outward from the high-pressure system. This high-pressure system pushes away clouds.

because the light is a great source of energy for the plants to survive. (i hope this )