The Data Don't Lie
I've lived in Portland for 123 days—three months of summer, one month of fall—and on 30 of those days there's been measurable precipitation. The most rain we've had in a single day is .65 inches. On 15 days—half of our "rainy" days—the bucket has delivered more than a tenth of an inch.

In the same period, my old hometown, Napa, has had nine days with measurable percipitation, totaling 1.58 inches. Maximum single day rainfall: .62 inches, with four of the days showing more than .10.

Conclusion: They were right; Portland is rainy.