Montana and Wyoming are infamous for their wind. My late father used to have a joke he liked to tell: "A Montana Wind Gauge is six feet of logging chain tied to the branch of a tree. If it's sticking straight out, the wind is blowing." (Logging chain weighs about six pounds per foot.) When my brother was still driving trucks, he got blown over in a loaded truck by the wind in Montana. When he called it in to the safety department - in most trucking companies having the truck tip over is cause for immediate firing - they were like "that happens. Get all your stuff out of the truck and we'll send someone to pick you up; we'll have another truck for you when you get here." They paid him for three days' home time to relax and he went right back out on the road. When the last decent governor Montana had was offered the chance to have wind farms erected in his state he announced that Montana's number-one natural resource is wind.

Given that they have serious wind in Montana and everyone builds with it in mind, how strong did the wind have to be to lift the EPDM membrane from a school roof?