You'll stand out like a sore thumb because you're from the South. You'll constantly complain there's no good food. You'll attempt to date following the customs you know from Outside, and they will fail miserably here. You'll wind up posting irked or confused or outright snarky anger that "The women in Seattle aren't interested in men." Or you'll wonder aloud at The Seattle Freeze. Or you'll just seethe silently as you collect fake internet points posting endless sunset pics in an attempt to convince yourself that you really are enjoying it here.
You'll complain about local drivers, complain about local bike riders, and eventually start complaining about locals in general. The passivity and friendly surface with utter harrowing alone underneath will gnaw at your soul over time.
You'll start to wonder if The Lonesome Crowded West was a profound album title.
On the plus side - you'll see people leave their windows wide open without screens and you'll freak out, then slowly begin to trust that there really aren't that many insects here, but then fall comes and you'll probably develop acute arachnophobia. On the other hand, being from Florida, you might just see Wolf Spiders everywhere and think "aw, they're cute."
Crowds .. you'll be good. We're not that crowded.
Over all ... my prediction is you'd be happier in Portland, as they retain that indie vibe and coffee culture that we once had, but are fast losing in our rush to build a big 21st century tech boomtown. You really are getting here a good 10 years too late for what you say you're after. Not that it's terrible here, just that you'll wonder who the fuck is building all these new buildings, and how will that be changing everything you like now.
Then you'll move to Portland.
As for "polar vortex" you seem to be confusing scary terms thought up by TV personalities with actual weather. The weather pattern that creates "the polar vortex" for the Eastern Half of the Continental United States is actually just the jet stream drifting far north to Alaska, then swooping almost due south along the Rockies to the Plains, picking up gulf stream moisture, then wallopping the upper Midwest and East Coast with super chilled, super snowy snowpocalyptic weather.
Note at no time in that did the phrase "West Coast" come up. Because we're not under the Polar Vortex. The same jet stream is actually doing the opposite here -- making our winters warm and dry. Of course, warm dry winters translates to fucked up dry forest-fire-and-water-rationed summers, but those problems mostly describe California and Southern Oregon more than they describe Puget Sound. We alone in the entire Continental US seem to have lucked out with global warming, at least so far. Our snow pack is down, but over all our reservoirs are still holding up.
So we're actually probably about the best place you could choose to live, if weather attacking you with cold is high on your list of Florida-expat concerns.