Right after Jim throws Hilda into the fallout shelter, a scene of their house suddenly becomes purple and blue and then goes black. this could catch people off-guard as it happens really quickly
When the bomb finally hits we see building bee destroyed sheep burning (not graphic at all) a church being destroyed a train going off the rails and a house getting demolished meanwhile during all this there's dark music in the background with continuous line by hilda concerned her cake will be burned.
The movie takes a slow approach to becoming incredibly heart-wrenching. It may be difficult to watch for people of any age, with its theme about the aftermath of a nuclear attack.