You should ask them that. Their cancellation policy would be in the contract you would likely sign.
If you are going at a time that is iffy, you may want to make contingency plans. For example, we left a day early for our last vacation to beat a storm coming in. I had booked a cancellable night in a hotel along the way in case that became necessary. In hindsight, we could have probably left as scheduled, but it eased my mind knowing that we wouldn't get caught on the highway and it got us to our destination a few hours earlier. It was an easier trip all the way around.
Sheila