Wildlife · Japan · summer
Synchronous Fireflies in Chichibu & Tatsuno Valleys
Synchronous firefly mating displays (Photinus carolinus and Luciola parvula), tracked directly from spring growing degree-day accumulation.
Readiness
Low confidence0
Season opens in 200 days
Live summary
As of 9 Nov 2026, Synchronous Fireflies readiness in Chichibu & Tatsuno Valleys, Japan is 0 out of 100, phase dormant. Degree-day accumulation is not shifting this score. The climatological peak is 16 Jun 2027. The timing model places peak on 16 Jun 2027. Mean cloud cover over the next three days is 42%.
- Readiness
- 0 / 100
- Status
- Dormant
- Confidence
- Low confidence
- Evidence type
- Historical estimate
- Model
- Climatological timing
- Timing
- Season opens in 200 days
- Estimated peak window
- 12 Jun 2027 – 20 Jun 2027
- Climatological peak
- 16 Jun 2027
- Adjusted peak
- 16 Jun 2027
- Accumulated GDD
- n/a
- Planetary K-index
- n/a
- NDVI
- n/a
- Cloud cover, next 3 days
- 42%
- Coordinates
- 35.99° N, 139.09° E
- Updated
- 9 Nov 2026, 08:42 UTC
The peak remains the climatological date, 16 Jun 2027.
Fourteen-day outlook
Projected readiness for each day. Botanical and wildlife bars use forecast temperature. Meteor shower bars combine stream activity, lunar phase, and forecast cloud cover. Aurora bars use the NOAA 3-day Kp forecast when available and a quiet-oval baseline with forecast cloud cover for days 4–14.
Mon 9
0 out of 100 on 2026-11-09
57% cld
Tue 10
0 out of 100 on 2026-11-10
62% cld
Wed 11
0 out of 100 on 2026-11-11
6% cld
Thu 12
0 out of 100 on 2026-11-12
2% cld
Fri 13
0 out of 100 on 2026-11-13
12% cld
Sat 14
0 out of 100 on 2026-11-14
51% cld
Sun 15
0 out of 100 on 2026-11-15
94% cld
Mon 16
0 out of 100 on 2026-11-16
34% cld
Tue 17
0 out of 100 on 2026-11-17
78% cld
Wed 18
0 out of 100 on 2026-11-18
76% cld
Thu 19
0 out of 100 on 2026-11-19
34% cld
Fri 20
0 out of 100 on 2026-11-20
60% cld
Sat 21
0 out of 100 on 2026-11-21
18% cld
Sun 22
0 out of 100 on 2026-11-22
29% cld
Field notes & historical context
Humid early-summer mountain streams west of Tokyo host Genji-botaru (Luciola cruciata) and Hime-botaru displays ahead of the East Asian plum rains.
Firefly pupation and adult emergence are governed by cumulative soil and air warmth since early spring; USA National Phenology Network and Great Smoky Mountains entomologists use growing degree days directly to forecast peak mating weeks.
35.99° N, 139.09° E · Asia/Tokyo
Sources & data freshness
Historical estimate · Low confidence · Updated 9 Nov 2026, 08:42 UTC
- Open-Meteo ERA5 & Forecast
Daily max/min temperatures (GDD base 5°C) and 14-day outlook
- USA National Phenology Network & NPS Entomology
Growing degree-day emergence thresholds for synchronous fireflies
Safety & responsible visiting
White light disrupts courtship flashing for up to several minutes. Cover all flashlights with red cellophane, point beams only at the trail, avoid DEET sprays, and never step off boardwalks onto larval leaf litter.
Natural phenomena depend on live weather, local access rules, and habitat conditions. Verify local advisories before travelling.
Ground-truth provenance
Community reportField observations for Chichibu & Tatsuno Valleys
Community observations supplement satellite and weather models with eye-level reports. Every submission is tagged as a Community report with provenance and moderation status—never blended silently into automated readiness scores.
No community field reports have been logged for Chichibu & Tatsuno Valleys in this session yet.
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