Somewhere between 20-30mph when it went down. The screen was acting as a sail, and the connections in the center part of the frame popped apart under the pressure of the screen bungeed to it when the wind wasn't going.
Garrett
When I am hired to do a job when the winds get to be anywhere from 15-20mph I call it off, as I have stated in my contract. It is not safe for the audience nor is it safe for my equipment. I am sure you learned the equipment lesson already.