If you're just looking for a healthy place to chill for a little while and recharge the batteries, ive spent the past 3 years living in my truck spanning the whole country.
Being winter, the best air quality and climate you're going to get is either Palm Desert, CA or the florida panhandle between Destin and Seaside. St George, UT is also good but it's at 3,000 ft.
As summer comes, Santa Cruz, CA and the nor-cal coast north of bodega bay are exceptional. Great climate, clean air, sun. Very sparsely populated though.
Savannah, Georgia is also pretty solid. Beautiful city as well.
Not sure where in the country you are but hopefully those help a bit