Mark, you might do a search on smoking while raining and find that the only real issue that arises is if it is indeed raining really hard(insane) some water will collect in the bowl of the WSM. It will tend to play around with the temp a bit but as always, the WSM will come back to temp and, well, stay there.
I used some white oak and hickery with a mix of Kingsford and K-Mart Briquettes.
The WSM was naked in the rain most of the night. I am hesitant placing it under the screen porch for these over-nighters. I now have only some aluminum foil over the top vent (rain stops). So far so good. My wife is ready to hurl, she hates the smell of smoked food in the morning.
I might toss the shoulders in the oven for the last 2 hours due to poor weather conditions.
Thanks for replies so early this AM. Have a great weekend.
Mark, good job with the foil on the top vent...when you open the WSM you will probably notice some water in it.
There is one terrible problem I see...you should think about getting another wife(ready to hurl due to smoked meat in the morning)mine loves the smell of the pork anytime of day and so should yours!!/infopop/emoticons/icon_biggrin.gif
Just kidding about the last paragraph(incase you couldn't tell)
Without further bandwidth I will say this; my pork shoulder turned out great. The people loved it and since the local BBQ place had a fire (closed all week) I think I was the only one in the state with pulled pork today.