You can use a Terminal command to disable Time Machine's local snapshot feature, which will delete all of the local snapshots on your internal hard drive. However, if you really need to delete those snapshots (which I don't recommend unless you desperately need that space), there is a way to purge local snapshots from your internal hard drive.

That being said, everything doesn't always work correctly, and you may find yourself out of storage space on your internal hard drive, and those snapshot backups won't go away. The program will then continue to replace the old snapshot with a new one until you free up space on your Mac's internal storage, at which point it will go back to saving weekly snapshots as long as space permits.

If you then, say, download some large program and your internal hard drive plummets to below 10% (or less than 5GB of internal storage), Time Machine will delete all local snapshots except the most recent. If everything is working correctly, Time Machine will automatically delete the oldest snapshot backups as soon as your internal hard drive has less than 20% of storage space left. First, let me preface this by saying that you shouldn't worry about those backups and the space they are taking up.

How to clear disk space on macbook air