Just a few of these insects – whether you know them as lightning bugs or fireflies – illuminating a summer sky at twilight is a magical spectacle. Imagine seeing thousands light up at the exact same time.

Each year, from late May to early June, certain species of fireflies glow in unison as a part of their mating process. Males flash for several seconds and then go dark, and the females respond in kind. If you travel to one of these spots in early June, you can observe the natural phenomenon for yourself. 

Great Smoky Mountains National Park - Tennessee

The Great Smoky Mountains National Park is probably the most commonly known spot for viewing synchronous fireflies, and as a result, availability is limited. Since it is such a popular event, you actually have to enter a lottery for parking several weeks prior to the peak viewing times. The lottery has closed for this viewing season, but the lucky people who secured spots can see the display until June 7. Check the Great Smoky Mountains National Park website for more details and to learn about the application process for next season.

Congaree National Park - South Carolina

See the synchronous fireflies from now until June 14 in the Congaree National Park just 30 minutes from the state capital of Columbia, S.C. Visitors do not have to reserve a spot ahead of time and there is no entrance fee. Optimal viewing time is between 8 p.m. and 10 p.m. and the viewing area is easily accessible on an elevated boardwalk trail just steps from the Harry Hampton Visitor Center. Scott Teodorski, chief of interpretation and a park ranger at Congaree National Park says the park welcomes several hundred visitors each year for the event. "Visitors come from literally all over the world to marvel at the splendor of nature as showcased by the fireflies," he says. 

Allegheny National Forest - Pennsylvania

Scientists discovered a species of synchronous fireflies in the Allegheny National Forest in 2012, and today, the Pennsylvania Firefly Festival celebrates the spectacle every year. Held in Tionesta, Pa., the free festival occurs the fourth Saturday in June from noon until midnight. This year, the festival will be June 25 and will offer live music, exhibits, arts, crafts, food, fun and, of course, fireflies. Primitive camping is available with prior approval.