Cloudy with a chance of moths: bogong swarms are bamboozling weather radars across NSW
News Source
β’Fri, 16 Oct 2026 23:00:14 GMT
π° What Happened
Weather radars across eastern New South Wales are showing widespread rain on many nights when no rain is falling. The likely cause is huge swarms of bogong moths.
The moths are flying towards the Australian Alps. The ABC's meteorologist said the fake rain appears almost every night, especially around Sydney.
Radars send out radio pulses that bounce off water in clouds. Moth bodies and wings can bounce the signal back too. A Bureau of Meteorology spokesperson said big numbers of insects can look like very light rain, mainly near sunrise and sunset.
π The Backstory
Bogong moths migrate long distances each spring to cool caves in the Alps, where they rest through summer. The journey is one of Australia's great wildlife events.
In 2000, during the Sydney Olympics, a swarm drawn to stadium lights was so big that meteorologists mistook it for rain. The moths are now listed as endangered, and numbers have fallen in some years. This season they are back in large numbers.
π― Why It Matters
It is a reminder that the moths are still making their huge journey, and that their numbers are watched closely because the species is endangered.
Weather radars across eastern New South Wales are showing widespread rain on many nights when no rain is falling. The likely cause is huge swarms of bogong moths.
The moths are flying towards the Australian Alps. The ABC's meteorologist said the fake rain appears almost every night, especially around Sydney.
Radars send out radio pulses that bounce off water in clouds. Moth bodies and wings can bounce the signal back too. A Bureau of Meteorology spokesperson said big numbers of insects can look like very light rain, mainly near sunrise and sunset.
Bogong moths migrate long distances each spring to cool caves in the Alps, where they rest through summer. The journey is one of Australia's great wildlife events.
In 2000, during the Sydney Olympics, a swarm drawn to stadium lights was so big that meteorologists mistook it for rain. The moths are now listed as endangered, and numbers have fallen in some years. This season they are back in large numbers.
It is a reminder that the moths are still making their huge journey, and that their numbers are watched closely because the species is endangered.