In our community in the mountains of central Arizona, the monsoons tend to be afternoon to overnight, but it’s typically pretty calm during the morning check-out hours. A guest should be able to look at the weather forecast (which, yes, can change on a dime here in the mountains) and be able to make an educated guess on when they should be able to depart safely before the next downpour or snow storm. If we are under a flash flood warning, I would let them stay for free, if possible, until it’s lifted.