On inselbergs and mountain masses within the tropics, the summits are frequently covered in cloud in locations where the orographic uplift of moist air is sufficient to cause condensation. If the upper slopes are covered in forest, the surfaces of the leaves and branches of trees act as collectors for condensed water vapour. This phenomenon is referred to as occult precipitation, because it does not relate to any rain-making process in the cloud itself and rain gauges placed outside the forest area will not record any rainfall.