Mayfly swarms in Hungary

In mid‑July 2026, massive swarms of non‑biting mayflies appeared over Lake Balaton. The insects formed bright evening clouds that confused regional weather radar, prompting scientists to advise tourists to reduce strong white lighting and keep windows closed after dark. The swarms, while intense, were less severe than the previous year and posed no health risk.

By early August, the phenomenon had moved downstream to the Danube, with large mating clouds observed near Budapest’s bridges and at Dunakeszi. Blue‑light barriers were installed on several bridges to keep the insects above the water and support their reproduction. The event sparked a cultural response: a photo exhibition and festival in Szentendre, workshops, and talks by ecologists and WWF Hungary on light‑pollution impacts and conservation. The mayflies, protected under Hungarian law, attracted both scientific interest and public tourism.

Overall, the 2026 mayfly emergence progressed from a radar‑affecting nuisance at a popular lake to a celebrated ecological event along the Danube, highlighting both the species’ environmental role and the need for light‑management measures.