April: The Smokies are one of the most biodiverse places in the U.S. for wildflowers, and April is peak season: trillium, phlox, violets and more than 1,500 flowering species in total. Waterfalls run high with spring rain.
June: Early June is peak season for the synchronous fireflies, and rhododendrons and flame azaleas bloom at the high balds.
October: Fall color works down the mountains all month, from high elevations early in October to the valleys by early November. It's the Smokies' second busiest month for a reason.
Permits and reservations
There is no entrance fee, but a parking tag is required for any vehicle parked more than 15 minutes ($5 daily, $15 weekly, $40 annual).
Parking tag: Required year-round for parking longer than 15 minutes. Buy daily/weekly tags on Recreation.gov or at park fee machines; annual tags from the Great Smoky Mountains Association. It doesn't guarantee a space.
Backcountry camping: A permit and advance reservation are required for all backcountry camping.
Frontcountry campgrounds: Reservations can be made up to 6 months ahead on Recreation.gov.