Wind chill is based on how temperature is felt on exposed skin. Basically, the heavier it blows, the quicker you want to cower under a down blanket or move closer to the fire. With the help of WINDSTOPPER® technology, the FlyliteTM Jacket effectively annihilates wind chill—and it does it in an incredibly lightweight, highly-breathable package. Less bulk. More warmth. Fish Longer.