Driving in 40 MPH winds is safe and possible as long as you keep both hands on the steering wheel and never take your eyes off the road.
If the wind starts pushing your vehicle around then you might want to drive a bit slower if it's safe to do so or pull over if possible until the wind calms down.
I've driven my vehicle in 40 MPH and even 60 MPH winds but sometimes the wind will start pushing my car around and then I will pull over and wait it out.
I once saw a car get pushed into the lane of an oncoming semi truck and the driver and passengers of the car died.
So if I do not need to drive I stay home and off the roads when the wind is above 40 MPH but if I do have to drive I'm very careful and watch my surroundings and keep both hands on the steering wheel.