As others have said, wind is the main thing to watch with WSM's......it will purr along with temps in the 40's.
I have a couple of welders blankets that do a good job blocking the wind (I wrap them around and use a heavy clip to fasten them at the top so that the top vent can still breath). That said, I only had to wrap them twice last year out of 30 comps. I probably should have wrapped them a couple of other times but I just turned them into stick burners when the fuel got low....
Fire Dancer BBQ
Don't Burn The Day Away.....