Synchronous firefliespeak tracker 2027
When do synchronous fireflies peak?
Synchronous fireflies usually peak from mid-May to mid-June across the 2 places we track. Congaree National Park, South Carolina usually May 11–Jun 20, per National Park Service and Great Smoky Mountains, Tennessee usually May 21–Jun 10, per National Park Service. The next season starts in ~7 months.
Updated Sep 28. Sources: National Park Service, Congaree fireflies ↗ (opens in a new tab), National Park Service, synchronous firefly research at Congaree ↗ (opens in a new tab), National Park Service, Great Smoky Mountains firefly viewing dates, 2026 news release ↗ (opens in a new tab)
Pick your travel week
Pick a week: the places where synchronous fireflies usually peak then light up. Usual windows from each place's own source, not a forecast.
Week of May 11
- Usually peaking this week
- Other weeks
Usually in peak the week of May 11
- Congaree National Park, South Carolina
Usually May 11–Jun 20
When the parks open for viewing, year by year
Neither park posts live firefly reports. Each announces a run of viewing nights weeks ahead, timed for the peak it predicts (the Smokies from soil temperatures). These are those nights, as announced.
Bars are the nights each park opened for viewing, announced weeks ahead as its predicted peak (not an observed peak). Empty rows: no announcement on the park's website.
Sources (16)
- National Park Service, Great Smoky Mountains firefly viewing dates, 2015 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly viewing dates, 2017 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly viewing canceled, 2020 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly viewing dates, 2021 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly viewing dates, 2022 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly lottery and viewing dates, 2023 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly lottery and viewing dates, 2024 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly lottery and viewing dates, 2025 news release ↗ (opens in a new tab)
- National Park Service, Great Smoky Mountains firefly viewing dates, 2026 news release ↗ (opens in a new tab)
- National Park Service, Congaree fireflies festival canceled, 2020 news release ↗ (opens in a new tab)
- National Park Service, Congaree firefly viewing, 2021 news release ↗ (opens in a new tab)
- National Park Service, Congaree firefly viewing event, 2022 news release ↗ (opens in a new tab)
- National Park Service, Congaree synchronous fireflies viewing dates, 2023 news release ↗ (opens in a new tab)
- National Park Service, Congaree synchronized fireflies viewing event, 2024 news release ↗ (opens in a new tab)
- National Park Service, Congaree firefly viewing event, 2025 news release ↗ (opens in a new tab)
- National Park Service, Congaree fireflies ↗ (opens in a new tab)
See two in one trip
Congaree National Park + Great Smoky Mountains
Usually overlapping: May 21–Jun 10
Congaree National Park → Great Smoky Mountains (about 200 mi). Straight-line miles; roads are longer.
Know before you go
- Great Smoky Mountains, Tennessee
Usually May 21–Jun 10
- Closures: Elkmont closed after noon on firefly nights (reservations and campers only) (May–Jun)
- Cost and permits: Cades Cove car-free Wednesdays (May–Sep)
- Cost and permits: Elkmont: The viewing area: open at night only to reservation holders and campers during the eight nights
- Cost and permits: Elkmont Campground: Registered campers can watch without a vehicle reservation
- Congaree National Park, South Carolina
Usually May 11–Jun 20
- Closures: Visitor center, boardwalk and front-country trails close at 4:30 p.m. on firefly nights (May)
- How do I get a pass, and what does it cost: Passes come by lottery on Recreation.gov, one entry per household, in early April. It's $1 to enter and $24 more if you win, $25 in all. In 2026 there were 145 passes a night, each for one car with up to 8 people; RVs, trailers, big vans and buses aren't admitted.
- Top spot: Firefly Trail: The designated trail for event nights; stay on it
Questions people ask
When do synchronous fireflies peak in 2027?
It depends on the place. In a typical year: Congaree National Park, South Carolina, May 11–Jun 20 and Great Smoky Mountains, Tennessee, May 21–Jun 10. Each place page has its own dates.
Where can I see synchronous fireflies?
We track 2 places: Congaree National Park, South Carolina (usually May 11–Jun 20) and Great Smoky Mountains, Tennessee (usually May 21–Jun 10).
How long does the firefly season last?
Across the places we track, from about May 11 (Congaree National Park, South Carolina) to Jun 20 (Congaree National Park, South Carolina). Each place's own window is shorter.
How many kinds of synchronous fireflies live in North America?
Only three of the world's more than 2,000 firefly species flash in sync here. Elkmont's is Photinus carolinus; Congaree's is Photuris frontalis, whose males flash quickly twice a second.Sources: National Park Service, Congaree fireflies ↗ (opens in a new tab), National Park Service, Great Smoky Mountains synchronous fireflies ↗ (opens in a new tab), National Park Service, synchronous firefly research at Congaree ↗ (opens in a new tab)
Why do the fireflies flash together?
It's a mating display, and researchers still don't fully understand the synchrony. One idea: females only answer when there is enough flashing, so males flashing together get more replies.Source: National Park Service, Great Smoky Mountains synchronous fireflies ↗ (opens in a new tab)
How do you track synchronous fireflies?
Each place moves through 3 stages: Beginning, Peak and Declining. Every stage we show comes from a dated report with its source, and every forecast lists its sources.
In season now:Fall foliage →Wildflowers →