I have had Add a rooms on a couple of campers and have used them in all kinds of weather. I would put the arms out in carport style, stake them down, then guy the awning with straps and springs. Then pitch the room. Never lost one and have had them up in 45mph gusty winds along the coast.
Now we use a EZup style shelter with screen or solid wall attachments. I believe mine came from Dicks Sporting Goods and I got the whole thing for ~$100 on their fall clearance sale.
If we hit a spell of really wet weather I can also string tarps. I have at least one 30x60
Aaron