We use the words "drizzling" or "sprinkling" here. They both mean "to rain or let fall in fine drops" If it's very, very light rain, you can use the word "mist". "Drizzling" usually implies a little harder rain than "sprinkling".

What is very light rain called?

Drizzle is a term used for a very light, fine rain. The drops tend to be very small and not very dense. Mist is similar to drizzle, only the number of drops in any given area is greater. ... Hail forms when rain droplets get pushed higher into the atmosphere by strong upward winds.

How do you say it's raining lightly?

“It's just spitting a little.” “It's drizzling.” Drizzling is more than spitting, less than raining.