Things to take into consideration are shelter and electricity. Most singers will require a power socket for their equipment. Most will bring a long extension lead, but it must be close enough to reach. I now have a battery-powered speaker to play in any area. The shelter is the most essential factor. Not only will this protect your performer in extreme weather conditions, but it also protects their equipment. Speakers, iPads and electricals can overheat and, of course, don't mix with water. You should work together with your venue and entertainer before and during the day, as the ever-changing weather may change the location of your singer ever so slightly.