Presumably it's not meant for the entire town. Just the people who are already in town nearby who have enough advance warning. It makes sense to be in a church

Presumably it's not meant for the entire town. Just the people who are already in town nearby who have enough advance warning. It makes sense to be in a church since that's in the center of town and you can lock the doors to give enough time for people to get into it and cover the entrance. If your family were at home in the nearby countryside they'd flee into the forest or something instead.