Make your repair as soon as it empties, as quickly as you can, then fill back up. If the water table is high in your area, i wouldn't drain.
I saw that you are in the desert, but i have to put that water table line in there for obvious reasons.
There is no duration of time that is ok to leave a pool empty that would apply across the board. And air temp would be different than direct sunlight on plaster. As well as humidity. There is more to it than just the water table. You may be able to get a pool company to take the risk of just draining for you, and you do the work. But i wouldn't