One of the major problems I've encountered with the vast majority of outdoor jobs is sunlight. Most of the jobs are late afternoon and on into the evening, and in many instances the sun is shining right in your face. I made a special hood to cover the keyboard display so I can see what I'm doing, but the LED lights above the various buttons become invisible in direct sunlight.
The other problem is heat. Today, the temperature is 101, thus working outdoors is brutal. I have two fans blowing on my at all times, and a half-dozen bottles of water in a cooler chest next to the keyboard - they're essential tools this time of year.
Fortunately, I can pick and choose most of the jobs and rarely do outdoor work these days. I'm just too damned old to subject myself to that much heat and humidity. Tomorrow's job is indoors, and the air conditioner will be running full blast. Weatherman says tomorrow's high temperature could hit 103 with a heat index of 110. The job was originally scheduled for outdoors, but they changed it to indoors because of the oppressive heat.
Another thing that must be considered is the effects of heat on your equipment. Some PA systems have thermal cut-offs, Mackie and Barbetta being two that immediately come to mind. Both now have small, cooling fans inside the cabinets, but when the PA is sitting in direct sunlight and temperatures are in the upper 90s, they can still shut down when you least expect.
Some keyboards also have thermal cut-offs. Those with external power supplies, such as the Yamaha PSR series, can shut down when the power supply temperature exceeds a certain temperature. Today, about 12-noon, when the thermometer soared to 101, I had to put on gloves to open the lock on my boat. That brass lock was too hot to touch without burning yourself. You can only imagine what the temperature must be inside a black keyboard.
Good Luck,
Gary