It does rain more on the weekends

 If you are in the northeastern United States, and yet another weekend has been ruined by rain, feel free to lean your head out a window and scream at a motorist. They are, for the most part, to blame. In 1998, a group of scientists at Arizona State University analyzed data going back to the 1940s, and found that a disproportionate amount of rain was hitting on weekend days. Since the seven day week isn’t natural, they went looking for some unnatural causes of the wet weekends.

There is a scientific reason why it always rains on weekends

The study, published in Nature, suggests that rain is most likely to occur along the US Atlantic coast on the weekend and the weather is most likely to be better on a Monday, Tuesday or Wednesday. The most obvious culprit is the “natural” cloud-seeding effect created by the massive drift of East Coast pollution, which also follows a well defined weekly cycle. Even Atlantic hurricanes may feel the punch of the workweek, according to the study.

http://www.scienceagogo.com/news/19980706131634data_trunc_sys.shtml