"It is raining" is a common way to say that it is raining in Engpsh.

For example:

"It is raining outside, you might want to bring an umbrella."

"It was raining heavily last night, so the streets are wet this morning."

You can also use the verb "to rain" to describe the action of rain falpng:

"It has been raining for hours, I hope it stops soon."

"It looks pke it is going to rain, I should bring my umbrella."