I have been known to fumble around the golf umbrella when an unexpected shower pops up! I also cut a hole in a small tin water pan and use that to cover the exhaust hole so rain doesn't enter the smoker. But generally, when rain is forecasted, I avoid smoking.
The pop tent, though, sounds like a perfect solution for smoking even if rain is in the forecast. I would just have to batten down the tent when the wind kicks up!