Our seasonal site is across from a farm and can be very windy on an otherwise windless day. We can walk 150 feet south to the lake and there isn't a breathe of wind, but on our site we could have 10 - 15 mph winds.
When we had our Class C, it had an electric awning that did not have a wind sensor. We used an awning tie down kit from Camco that came with anchors and heavy duty springs. Our awning was only 11 feet long, but the tie downs worked very well. The springs allowed the awning to move gently in strong winds so the awning fabric doesn't tear.
We still have the tie down kit and used it with our current TT, but it's a manual awning.
-Michael