Il pleut beaucoup.
Eel pluh boh-KOO
It rains a lot.
Simple
Il pleut très fort, mieux vaut rester dedans.
Eel pluh treh for, myuh voh reh-STEH duh-DAHN
It rains very hard, better to stay inside.
mieux vaut = it's better to, common structure
Il pleut des hallebardes, on ne voit plus rien dehors !
Eel pluh day al-BAR-duh, on nuh vwah ploo ryahn duh-OR
It's raining halberds, you can't see anything outside!
pleut des hallebardes = archaic but charming idiom meaning violent rain
More French Weather Phrases