“What many movie buffs don’t know is that George Bailey’s bleak Christmas Eve was actually shot during a series of 90-degree days in June and July in 1946 on RKO’s ranch in Encino, California. The days were so hot that Capra gave the cast and crew a day off during filming to recover from heat exhaustion. In the famous scene on the bridge, before he saves Clarence the angel from the dark, swirling waters below, a suicidal George Bailey is clearly sweating — although Jimmy Stewart’s wonderful acting convinces us that fear and dread might well be the reason for that.”
Films made prior to this one used cornflakes painted white for the falling snow effect. Because the cornflakes were so loud, dialogue had to be dubbed in later. Frank Capra wanted to record the sound live, so a new snow effect was developed using foamite (a fire-fighting chemical) and soap and water. This mixture was then pumped at high pressure through a wind machine to create the silent, falling snow.