When we call for "Rain" (as in, "Rain at Times", "a rainy day", "Occasional rain") is a more widespread event. Most, if not all, of the area will see rain and it"ll last for a while.

"Showers" are more scattered. That usually means that not everyone will be getting wet at the same time. It could be raining in Everett and Gig Harbor, but dry in Seattle and Arlington. Plus, showers tend to be much shorter in duration – anywhere from a minute to an hour.