The loss of water from the aerial parts of the plants specially through the stomata is known as the "Transpiration".
Trees and other plants use water in their photosynthesis; the excess is returned to the atmosphere. This raises the local humidity, which is why woodlands sometimes seem "stuffy" compared to nearby grasslands.
transpiraton can effect climate of an area as the no. of tree will be more so no. of transpiration would be faster which can form a more heavier cloud that can be the reason of rain.... due to large no. of trees in monsoon forest it almost experience rain