Why Are Raindrops Different Sizes?

Cloud droplets start tiny

Clouds contain tiny droplets formed on particles such as dust, salt, or smoke. In warm clouds, droplets grow as they collide and merge. In mixed-phase clouds, ice processes can also help precipitation particles grow before they melt into rain. [1]

Collisions make a range of sizes

Droplets encounter different neighbors and air currents. Larger ones generally fall faster and can catch smaller ones. Updrafts may carry droplets upward or slow their descent. The resulting drop-size distribution matters to meteorologists because it affects radar measurements. [2]

Why large drops break apart

Air pushes against a falling drop. Small drops remain close to spherical, but larger ones flatten underneath as aerodynamic forces increase. The largest drops become unstable and break into smaller drops. NASA describes fall speed as increasing with size up to a maximum for the largest drops. See also how fast raindrops fall and how rainbows form.

Frequently asked questions

Frequently asked questions

Are raindrops shaped like teardrops?

No. Small drops are nearly spherical; larger drops flatten underneath as they fall.

Why does heavy rain have larger drops?

Cloud growth and collisions can create a range of drop sizes, but rain rate alone does not determine every drop’s size.

Can weather radar measure drop size?

Specialized radar and instruments can estimate drop-size distributions, but each method has limits.