During dry spells bees need water and go looking. They prefer "natural" water that has minerals and such; water we might consider dirty. We arranged a flagstone in a planter so the air conditioner drip water would fall through a bush and on to the stone. The water never gets deep and has moss and plant matter that bees tend to prefer. The flagstone is sitting on big river rocks so the water does not pool and it all dries out when the AC's off (avoiding mosquitoes).