Woofie, it's really quite sturdy; the frame is made of steel and we anchored it down with screw-in ground anchors. It also has "flaps" at the bottom that you bury with soil to keep air from getting up underneath. We've had some pretty strong winds and when everything is zipped up it doesn't even budge. (if the end doors were left open, that would definitely be a different story!) My biggest concern is snow in the winter -- I'm planning to put some supports under the hoops to keep them from bending down.
