It's not your imagination that you seem to find more potholes every spring. Nyquist notes that small cracks form in roads due to typical wintertime traveling and the relative lack of road crews performing repairs. Water, from rain and snow, fills the cracks, then freezes, expanding as it does so. That opens the way for more weather to get down there, so you now have water under the road. Then that freezes.
Spring comes, things thaw out, and the ground gets softer.
Trucks come along and mash the soft spots down, and you have a pothole. To reach Dr. Nyquist, contact the News Bureau.