you could try hanging a weight from the window. Not too heavy so it will open when needed, but heavy enough to hold it closed in a wind storm. I tied a string around a brick and am using it on mine

Thanks for the idea. I've placed mine out Sunday evening, we had some strong southerly winds earlier this week (sustained 20-25 mph, gusts 30-35 mph). I didn't have anything in place to keep the lids down and there were no signs of damage (I wasn't home during the peak wind conditions). But I think it is best to take some precaution, especially since the arm can open up to 15 lbs......a 5 lb. weight should be a good balance.

Another suggestion:
1. Make a magnetic clasp to attach the autocloser to the lid.

2. Attach a cable or chain to the lid that lets it open just past the range of the autocloser but not enough to open vertically.

If the wind catches the lid when open, it will disengage the autocloser and fall shut. You will have to reconnect the clasp later.

This also allows you to open the lid for access by disconnecting the magnetic clasp and the chain.

Rick