The idea of the iron "cap" is good if there is a possibilty of rain, but I wouldn't deliberately use the unit if it was raining. However the rain possibilty existed I would use the elbow and take a piece of aluminum foil and cover the thermostat knob area to keep water out. I started my pork butt only to have brief light showers threaten. I used the aluminum foil over the knob area and the smoking continued. There was no effect on the smoking time,etc..