The difference between drizzle and rain

The two forms of liquid precipitation, drizzle and rain, are classified in a number of ways depending on the size of the drops, the visibility associated with the precipitation and the rate at which it falls.

Drizzle, which is defined as drops with diameters less than 0.02 inches falling close together, usually falls from stratus clouds. The relatively thin stratus clouds have slow, upward moving air currents. In these conditions, cloud droplets have little time to grow before they become too heavy for the air currents to support. The drops fall to the ground, appearing to float in air currents. As seen in the graphic above, the intensity of drizzle is based on the visibility at the time the precipitation is falling.

Rain, which is composed of widely separated drops with diameters usually greater than 0.02 inches, generally falls from towering cumulus clouds. The cumulus clouds, with fast, upward moving air currents, allow cloud droplets to combine and grow. Raindrops can reach sizes up to 0.25 inches before falling to the ground. The intensity of rain is based on the amount that falls in one hour. The intensity can also be estimated visually.