Wind is the biggest temperature killer on the WSM, well rain and wind is worse, but as a single factor I rate the wind the worst.
You might make yourself a two fold wind break, basically three sheets of ply hinged like a folding screen, if you make them long enough you can make a triangle out of it to surround your pit.
They only need to come level with the top of the lid, you don't need massive height.
If you can only open the vent away from the direct wind, that helps keep temperatures stable, as the cooker isn't having a pressurized air forced fire one moment, and not the next.
You might make yourself a two fold wind break, basically three sheets of ply hinged like a folding screen, if you make them long enough you can make a triangle out of it to surround your pit.
They only need to come level with the top of the lid, you don't need massive height.
If you can only open the vent away from the direct wind, that helps keep temperatures stable, as the cooker isn't having a pressurized air forced fire one moment, and not the next.