it was raining
Comme il pleuvait, nous avons dû manger notre pique-nique à l'intérieur.
Since it was raining, we had to eat our picnic indoors.
It rained every day.
L'autre nuit où il pleuvait, tu l'as vue se faire tuer, non ?
That other night when it was raining, you saw her get killed, didn't you?
— Memories of Murder (2003)
Je restais à la maison comme il pleuvait.
I stayed home as it was raining.
Il lui serait difficile de revenir s'il pleuvait.
It would be difficult for him/her to come back if it rained.
— Les Enfants du temps (2019)
Hier il pleuvait, aujourd'hui il fait beau.
Yesterday it was raining; today the weather is nice.