Spring cleaning has become nearly ritualized in the West. Makers of cleaning products ramp up advertising late in the winter. Internet sites and magazines become awash in spring cleaning tips. Public service campaigns for everything from properly disposing of outdated pharmaceuticals in America to removing litter from t­he Irish countryside are attached to spring cleaning each year. It's kind of an unconscious, collective movement. ­The reasons behind why we spring clean are rooted in two cultures, Jewish and Iranian. A third, the Chinese, also have a similar custom. All of these traditions extend far­ back into the distant past.

Source: How Stuff Works