Conditions should be good Sunday aside from the deer flies. It is supposed to be more mild and less humid, so conditions should be better. For the first time in many years, I've laid off the trail this past week due to the flies (humidity, heat...) and been riding dirt roads with my cross bike -- much more refreshing.
Ride fast. Wear baggies because they bite thru lycra. Keep mouth closed while riding. Don't stop due to mechanicals or rest. Wear head covering and put a helmet cover on your lid so they don't fly into your helmet vents and bounce around. Consider using deer fly tape on the helmet. Wear light colors and take a shower before you ride so you don't stink and attract more flies.