Yes I agree fully with Other Clive. Take bad weather seriously when you are caravanning. Especially during the winter months when weather can change in an instant. Remember that caravans can and will move in high gale force winds, and enough rain bulging in an awning roof WILL collapse the awning, and buckle poles beyond repair, apart from ruining everything inside the awning.
Getting up at 4am on a freezing cold winter morning to deal with a rain bulged or wind wrecked awning is NO joke at all. Setting it up can be time consuming, especially with the larger awnings, and I'd consider extra sets of roof and ground support poles for longer length awnings to reduce the spans between them. It's worth the extra effort to get it right.
As to pegs, buy the longest and strongest you can get hold of, and anchor them firmly. Government surplus stores are good sources of 'proper' pegs. Plastic ones.....forget them. Lovely in the height of summer in good weather but otherwise...totally useless. If you are on a particularly windy site then use steel 'marquee style' metal stakes to anchor the caravan legs down as well as the awning. Chuck out that silly 'guy rope string' that the awning manufacturers give you. It's a complete waste of space. Get some real rope and anchor it to some substantial guy rope pegs.
That way, you can lie there listening to the wind howling, and the rain lashing your caravan without a care in the world.