Last time I checked it was only a little over an hour from West Lafayette to Chicago, and it is not a 20 degree difference between the two cities (right now). Anyway, yeah, it probably did get pretty close to zero a few nights there (it did here). The pics don't work, and I am not trying to be your mom, I just hate to see people have nice cars and do a half a$$ job when they do stuff to them. I had a friend in highschool that did that and it pi$$ed me off all the time. I'm not saying you have to put the filter on the AIR tube, but have you ever made fun of a Honda with an unpainted body kit? Its the same principle. I guess I just take more pride in what I do.
BTW, if you don't want to use a filter, you could just duct tape it shut.