It's so interesting, isn't it? English and Romance languages both have gerunds (the "is" plus "-ing" construction), often used to express continuous actions interrupted by something - "I was talking when someone rang the doorbell"/ "Sto parlando quando qualcuno ..."
But while English uses a gerund for "it is raining" (presumably because in England rain is often an ongoing, continuous state), French and Italian just use the present tense "il pleut", "ce piove".