I often see reports of rain north of Seattle...but nothing is falling down in Olympia. Can there be that much of a difference?
Yes! It depends upon the weather pattern, the movement and position of the jet stream (or what we also call the steering currents). If the jet stream is positioned closer to the Canadian border, the area from Seattle north will tend to get more rain than points farther south...such as Olympia. But if the jet meanders farther south, then Olympia will tend to get wetter. On average, the Olympia area tends to get more rain than Seattle (for example)...but localized patterns such as a Puget Sound Convergence Zone can produce more rain north of Seattle than in Olympia. The interaction of weather with terrain creates many such examples.