The turn of the seasons here is accompanied by a variety of visual clues. Changing leaves, darker clouds (usually rain but every now and again snow instead), and of course shortening days and warmer clothes. Each season also comes with it's own set of smells, and these for me help me to get more into the season than almost anything else.
Spring and Summer, for example, are accompanied by the smell of mown grass. The other day it was warm enough for someone to be getting in one last mow. (Not me, though my lawn could probably use it, but I have decided now that we've had a frost not to worry about it.) Even though it was October, it brought Spring to the forefront of my mind. Cookouts are one of those Summer smells, as in the unique smell of the beach - which around here is normally a pleasant thing.
Winter's smells, by contrast, are almost all indoor smells. Snow, for example, doesn't have much of a smell. Unless you have dogs, and in that case you shouldn't be out and about in that snow anyway. White snow only. Pine might be an outdoor smell, but of course in Winter you usually get that indoors around the Christmas tree. Being out in an actual pine forest has the same smell, but being evergreens it doesn't matter much the season. Other smells include those of holiday foods, such as pumpkin spices.
For Fall, that smell is a combination of things, but none are more prominent, more welcome to my nose than that of wood smoke. Something about catching that first whiff on the breeze lets me know that fall has truly arrived. Couple that with the smell of apples, particularly apple cider, and even if I couldn't see the leaves change I'd know what season it is. Now, I realize this may be a regional thing, and that if you live in Southern California the smell of wood smoke might mean something far less pleasant, but up here (relatively speaking) that smell means the temperature is dropping and people are turning to their wood piles once again.
That, for me, is one of the biggest appeals of a fireplace, too. Yes, they're pretty and provide warmth, but it's that lingering smell, especially if you're burning more fragrant woods, that really sells the experience for me.