Potholes are a sign that the street pavement is wearing out. Over time, pavement cracks and breaks due to moisture build up or wear and tear from traffic. Water trapped between the cracks may cause erosion under the surface and cause the pavement to sink down and break, resulting in a pothole. During winter, water under the pavement freezes and expands, then thaws and contracts. This freeze/thaw cycle accelerates the rate of pavement deterioration and increases the incidence of potholes, making them more prevalent during winter months.
When it is cold or wet outside, the material used to patch potholes does not adhere well to the surrounding pavement. Pothole repairs made under these conditions may not last very long but are necessary for safety reasons. More permanent street repairs takes place in the warmer months when hot asphalt becomes available.