I dug mine(with the excavator) in mid september, before any heavy rains. I am on the west coast, so rainfall and water tables are highly seasonal. I think this was pretty ideal timing, but I would ideally have been ready to dog by late august in case the rains were early.
I hit water in gravel at about 17ft, and solid rock of some sort, as far as I could tell, at 19ft.
The water level came up about 7ft from the bottom at that time, overnight; it
rose no higher, and would recharge overnight if drained. My casing is 50" inside diameter, so this is a good amount of water, the availability of this much will inform the rest of my water system design
A month later, the water level is at least 5ft higher. I expect several issues would result if I was digging now.
1) Unclear if the water level and recharge rate I discover now will be adequate at the end of the dry season.
2) Hard to keep digging with a hole full of water.
3) Increased issues with sides of hole collapsing and spoil washing back into the hole from heavy rainfall while pit is open.
Some of these issues may not apply with the method you have in mind, but my connection isn't up to viewing the video!