Lake Balaton mayfly swarm disrupts radar and summer visitors

Massive swarms of non‑biting mayflies (árvaszúnyog) have reappeared over Hungary's Lake Balaton. The insects form bright evening clouds that confused the regional weather radar, producing a cloud‑like echo that initially was thought to be water vapor. The swarming typically begins after 9 p.m. and can last until midnight, potentially persisting for several weeks, though this year the intensity is lower than last summer.

Experts from the Balaton Limnological Research Institute note that mayfly larvae help clean the lake’s sediment and serve as food for fish, waterbirds, swallows and bats. They advise tourists to reduce strong white lighting, use warm‑tone LEDs, keep windows closed after dark, employ fans or mosquito nets, and avoid heavily lit waterfront dining areas to lessen the insects' annoyance. The insects pose no health risk and are protected from mass eradication.