I wouldn't say wind is the worst because I hate riding in pouring rain, lightning, snow and ice. However, wind is the worst weather condition that I frequently ride in. Like others said, wind is worse than hills because at least you get a downhill when climbing. Of course, tailwinds exist in theory but I rarely ever seem to encounter them and crosswinds are almost as bad as headwinds. This morning the wind was howling out of the west, and I had perhaps 2 miles of tailwinds out of my entire 15-mile commute. About 5 miles was directly into the wind, and the rest was crosswinds. I suffered.