We camp seasonally directly across from a farm. Our site might have 20 mph winds with gusts to 30 mph, but walk 150 feet north past the farm to the lake and there is no wind. We have to tie our awning down or we wouldn't be able to use it.
We purchased this
Camco tie down kit. With our previous Class C with electric awning, coffee cans with cement would not work, they'd get thrown around easily. Maybe 5 gallon buckets with cement might have worked. For an electric awning, the springs in the kit allow the awning to move gently. The springs are 7" long and tight, but they do allow movement which keeps the awning fabric from getting torn. In really high winds, the awning might move a lot, but we've never had any issues. We had a really bad storm roll through a few years ago. The springs got completely over stretched and were no longer usable, but the awning survived. Camco does sell replacement springs.
Our current awning is manual. We use the same kit, but I'm not sure the springs are necessary since the manual awning doesn't really move in the wind like the electric did. We did have a storm roll through in the middle of the night last season that brought 60 mph gusts. The storm hadn't been forecast at the time we went to bed, but the Tornado Watch alert on my smartphone alerted us around 5:30 am. It was too late as the storm had already kicked up. No tornado for us, but one did touch down about 50 miles north of us. The awning was out and it survived that storm.
If you don't expect high winds when you are camping, the coffee can with cement might work for the occasionally dust up. If you have an electric awning and expect winds, I'd want something with more weight than a coffee can with cement.
-Michael