I think I have found the equation for transitioning-weather outfits! There are 3 main parts of an outfit and if you keep 2 of the items for your current season and switch out the third to the next or previous season, you'll have something that works.
Shoes + Bottom + Top
2 are for your current season, and 1 is for the next/previous season
For example, you have boots, jeans, and a sweater - switch out the boots with sandals, the jeans with a skirt, or the sweater with a tank top. In the spring you'd wear a dress and sandals - switch out the sandals for booties like I did here, or throw a trench coat over the dress. Obviously there is room for interpretation and you should wear what's comfortable, but I think this is a great way to start.