As Simon says, the client sometimes closes the deck at wind speeds less than 60 knots, however, sea state is also important on a H & S basis as to the ability to launch a rescue craft in the vicinity of the installations. Then you run into the fact that certain offshore rescue crafts will operate to different sea states so you get different limits. (Well that is what used to happen in the days when I used to fly the NS)
Funnily enough wind speeds didn't concern me as much as the Icing Level not counting turbulence problems). I think the many discussions of whether you should go or not in the crewroom were lengthy and varied. In my day, Management never wanted a straight forward flow chart which ended up "Go" or "No Go" as it took away the decision making of the crews. Well that is what I was told. That side of flying I don't miss..........
JohnW