The maximum wind speed for wind turbines is around 30 to 40 miles per hour and anything above 40 miles per hour wind speed could potentially cause damage to the wind turbines.
When wind speeds get to 50 MPH the wind turbines are shut down to prevent damage because at 50 MPH wind speeds and above severe damage can be caused to the wind turbine.
The high wind speeds can cause the blades to fly off through the air or burnout the generator by creating too much electricity.
So when the wind speeds are forecast or get to 50 MPH the wind turbines are shut down to prevent damage.