The best time of year to perform crack filling is in the fall and spring because crack thickness is at its median point. Asphalt material expands in hot weather and contracts in cold weather, so in the spring and fall, cracks will not be at their widest or narrowest. If we fill cracks in the summer when cracks are at their narrowest, the amount of material in the crack may not be sufficient to keep the crack sealed when the pavement contracts in the winter. Likewise, if we fill cracks in the winter, we may have too much material such that in the summer, the material will bulge out and be increasingly likely to be torn out by crossing vehicle traffic. In the Puget Sound, this is not as critical because we don’t experience the wide temperature swings between seasons like other places such as the Midwest. Consequently, the variance in crack openings is not as large.