The wind gate is an acupuncture point on your upper back (specifically UB 12 called Fengmen in Traditional Chinese Medicine). The wind gate is often referred to as your upper back and neck region. It is a very vulnerable area for invasion of external wind, which can easily lead to a cold - stuffy nose, sneezing, chills, headache, body aches, cough etc. Exposing this area to the elements of the weather (ie wind, cold, damp) can increase the chances that you will get sick.
Covering up the nape of the neck with a scarf, hood, or turtle neck can be very useful in this cold and windy weather! A simple way to add a bit more protection from the 'all dreaded' cold and flu season.