I've only ever driven through Concrete so can't speak to it. There is only one other decent sized town on Hwy 20 to the east (Marblemount). Beyond that you are looking at miles of wilderness. I'm not sure if the Hwy 20 pass has opened for the summer yet - they may still be plowing it out from under 5+ feet of snow. But you'll be limited to Hwy 20 west of Marblemount due to the winter closure. Sedro-Woolley (SEE-dro WULL-ee) is a nice small town. Like a Boone or Story City feel. Mount Vernon/Burlington is definitely the hub of the county. I'd say it's like an upscale Marshalltown. Small town feel, some depressed areas, a significant Hispanic population, but more/better commerce (i.e. newish Costco, Best Buy, Bed Bath & Beyond). You can run up to Bellingham for anything and everything (think Cedar Falls with more/better hipsters - Western Washington University is there, the state's 3rd largest public school).
The whole area is beautiful. You've got dense old growth forests and mountains, wide open spaces with farms in the Skagit Valley (SKA-jit), and salt water and beaches all within an hour's drive.
Most residences out here do not have A/C so you'll want some fans for the two weeks its warm out here (ie 85+ degrees). But it's not very humid and it still gets down into the 50s overnight. Basically the dew point is always like 55deg due to the cold Salish Sea - if it's warmer than that, it doesn't feel humid. But for the 6 months out of the year it's close to or below that, it's humid/foggy/misty/drizzly (or snowing at elevation). I know Concrete gets more snow than Mount Vernon, but I don't know how much. Above 4000 ft you're looking at 6+ feet of snow annually. Mount Vernon is only 200 - 500ft above sea level, and we only get measurable snowfall every few years.