I have had a couple nights that rain was coming down so hard that I was worried about how much water would get in my Big Green Egg while I was smoking a pork butt. One night, I had to move our patio umbrella to the deck and it was raining so hard that it kept falling over. I had to get cement blocks to hold it down.
I started looking for a solution to this problem and ran across the perfect solution. The SmokeWare SS Vented Chimney Cap for the Big Green Egg is a stainless steel cap for the Egg that prevents water from dripping into the vent holes. The instructions say you should attach the Nomex Chimney Felt to the top of the Egg, but I attached it to the inside of the Cap. This allows the Cap to be easily removed from the Egg so you can use the old Daisy Wheel Cap when you want.
It has rained a couple of times since I bought its and it works great. I would highly recommend it for anyone with an Egg.