Year round wind is the enemy. It can blow ash on your food, cause your temp to spike or more often suck the heat from your cooker regardless of season to outside temp.
remember that even if it's 95 F outside, that's still 150 F cooler then your cooking chamber. The more wind that runs by your cooker the more heat will be pulled away.
By no means to you need something large, but if you have to cook on really windy days then its a godsend.