With seasons comes a change in weather and, in turn, the change in daily life for people. School is upon us -- getting ready for it, or getting our children ready for the school year -- which takes time and energy. Usually time and energy AWAY from something else, such as reading blogs ;)
The days are getting shorter. I have a lamp that is supposed to help with seasonal disorder -- the lack of sunlight thing (but it was inexpensive so I don't know that it really works). I may have a mild case, but others can be deeply depressed by the lack of sunlight. And though I speak of retiring to Ireland, I've never been there and Denver has 300 days of sunshine. What would all that gray do to me? And my office faces south, which means that I should start getting sunlight about the Equinox, and the sun doesn't shine in during the hot days of summer, but is always a friend in the winter.
So, what season is affecting your characters and how? Do they love the renewal of spring? Are they caught slogging through mud? Is the shortening winter days filling them with dread? Are they flying with a summer breeze? Exultant at the change of colors of the leaves and the brisk snap of air?
Seasons affect us as people, and they should affect your characters, too. Use them.