There's a reasonably high earthquake risk, more likely to happen in your lifetime than a volcano.

On the social side, Seattle tends to be somewhat slower paced than SF or NY. You might not see the same level of high intensity and fast paced tech development that you find elsewhere, and might feel like you're moving slower than you want. There is an oft-noted 'seattle freeze', where people are polite, but reluctant to form close friendships - meaning that you might have more trouble finding the same strong friendships and communities that you can elsewhere.