In
the lowest 10 km of the atmosphere, temperature decreases with height. So when warm air rises from the surface, it cools. Because of the Clausius-Clapeyron relationship, this often means that the air is quickly brought to saturation. Condensation begins, and clouds form. If the air is especially buoyant, condensation continues, causing the water droplets to increase in size.
Eventually the water droplets are so large they begin to coalesce and fall as precipitation. For this reason, rising motion is often associated with precipitation.