Keep some extra blankets in your trunk.
This winter is supposed to be one of the coldest in recent years. I just read that there's even snow in Las Vegas! Last night I was out driving with my mom and my sister and we spotted a homeless woman on the sidewalk trying to keep warm. For once I was happy with my mom for having such a messy trunk. We dug through and found an extra blanket and a sweater to give to the woman who was incredibly grateful.
We all have extra warm stuff around the house. If you keep it in your car, chances are you'll find someone who needs it. There's no time like the holidays for giving and warming up someone else's night.