Denmark issues beach alerts over jellyfish bloom and impending thunderstorms

Marine scientists report an unprecedented surge of jellyfish in Danish waters this summer. The bloom includes unusually many moon jellyfish (brandmænd), sea nettles and the invasive lion’s‑mane jellyfish, appearing up to two months earlier than usual. In the Limfjord, densities have reached about one jellyfish per litre, prompting divers to abort outings because of concentrations of 20‑30 per square metre.

The Danish Meteorological Institute has also warned of heavy rain and thunderstorms on Sunday and Monday across much of the country, from Zealand and Bornholm to parts of Jutland. Lifeguards advise beachgoers to leave the water and seek shelter, noting that lightning can travel up to 100 m and pose fatal risks. Recommended actions include packing belongings, moving inland and avoiding open terrain until the storms pass.