Примеры

it is snowing - идет снег;
it is snowing a little - идет снежок;
it is snowing heavily - снег валит;
it is snowing, it snows - снег идет;
it is snowing. - идет снег.;
it snows, it is snowing - идет снег;
it was past midnight and what is more it was snowing - было за полночь, да и снег шел;
snow is falling, it is snowing - снег падает;
снег идет - it is snowing, it snows;