@HaikuHedgehog Fireflies start to appear in the US when temperatures are consistently above 65°F (18°C). For most of the US, that typically happens in late spring or early summer. Fireflies can be seen in abundance as late as September in some places.

@HaikuHedgehog @Alfred
There's an official event in Appalachia next month; the bugs are synchronized. They just are I don't make the rules.
https://www.nps.gov/grsm/learn/nature/fireflies.htm