If you’ve happened to glance at the Bureau of Meteorology’s radar over the past few evenings and seen what looks like rain settling across the New South Wales coast, only to step outside and find a perfectly dry, starry night, you’re not imagining things. You’re not the victim of a glitchy weather app either. The strange mismatch between what the radar is saying and what your own eyes are telling you has a surprisingly simple, and rather beautiful, explanation: bogong moths. These native Australian insects are on the move, and in such vast numbers that they are fooling one of the most sophisticated systems we use to predict the weather. It’s a wonderful reminder that technology, for all its cleverness, can still be surprised by the natural world. The Bureau of Meteorology has been recording what looks like evening rain along parts of the New South Wales east coast, but those patches on the map aren’t necessarily droplets falling from the sky. They might be millions of delicate wings beating through the warm air, migrating through the night and getting caught in the beam of radar systems designed to track weather, not wildlife. It’s the kind of story that makes you look at both your phone screen and the night sky with renewed wonder, because somewhere out there, between the radar echoes and the clear skies, an ancient journey is taking place.
The explanation from the Bureau of Meteorology is both straightforward and strangely poetic. A spokesperson told the Newcastle Weekly that it is possible the radars across eastern New South Wales are detecting bogong moths, and that large insects gathered in swarms could look like light, widespread rain—especially around sunrise and sunset. That last detail matters, because those are the times when the moths are most likely to take to the air or settle down, and also when atmospheric conditions can make radar beams behave in quirky ways. The Bureau was quick to point out that this is not a case of malfunctioning equipment. Radar technology is designed to pick up “echoes” from all sorts of things, not just rain. Buildings, birds, insects, even temperature gradients in the atmosphere can reflect signals back to the radar dish, creating patterns that look like precipitation. The key is knowing how to interpret those signals. Some of the more modern radar systems, like the ones at Terrey Hills and Yeoval, have what is called dual-polarisation capability. That means they send out and receive both horizontal and vertical waves, giving forecasters extra information about the shape, size, and behaviour of whatever is in the sky. With that richer picture, it becomes much easier to distinguish between an approaching storm front and a cloud of migrating moths. Newcastle’s radar, unfortunately, is not in that category. It is an older single-polarisation system, which means it doesn’t have the same ability to filter out non-meteorological targets. So while some radars can quietly subtract the moth signal from the weather picture, Newcastle’s cannot, and the result is a display that sometimes makes it look as though steady rain is falling when the skies above are perfectly clear.
To understand why the moths are causing such a stir, it helps to know a little about their strange and epic lives. Bogong moths are famous in Australia for undertaking one of the great insect migrations on Earth. Every spring and early summer, millions of them leave their breeding grounds in southern Queensland and other inland areas and fly hundreds of kilometres towards the cool, dark caves of the Australian Alps. There, they spend the warmer months in a kind of summer dormancy, gathering in massive clusters on rock walls, waiting for the heat to pass and the seasons to turn. It’s a journey that has been happening for countless generations, guided by the stars, the Earth’s magnetic field, and probably a good dose of inherited instinct. This year, however, something went a little differently. Unusually strong westerly winds swept across the continent, and the flying moths were pushed off their usual course. Instead of heading towards their mountain hideaways, they ended up drifting over the suburban east coast, bewildered travellers in a landscape of streetlights, houses, and gardens. For anyone living along the coast, this has meant more than just a curious radar anomaly. People have been sharing videos and photos of moths clustering around porch lights, fluttering through backyards, and resting on windowsills. A “Bogong Moth Tracker” has been quietly gathering sightings, and social media platforms are full of ordinary Australians trying to make sense of this sudden influx of winged visitors. It’s one of those moments when a natural phenomenon that usually happens far away from human attention suddenly walks into our daily lives and asks us to pay attention.
There is something bittersweet about this story, because these moths are not just random insects from the bush. They are officially listed as endangered on the IUCN Red List of Threatened Species, and their decline has been a source of real concern for scientists. For much of the year, bogong moths play a vital but quiet role in the ecosystem. They pollinate native plants, they help cycle nutrients, and, critically, they serve as a key food source for the endangered mountain pygmy-possum. That tiny possum, which lives in the boulder fields and rocky slopes of the Alps, relies heavily on the annual influx of moths to fatten up and raise its young. So when the moths disappear, or when their numbers crash, the effects ripple far beyond the moths themselves. This migration is not just a spectacle; it’s a lifeline. That’s why the recent swarms on the coast have been met with a mix of excitement and concern. On the one hand, seeing so many moths is a heartening sign that nature still has some resilience left. On the other hand, the fact that they were blown so far off course is a reminder that even the oldest, most reliable rhythms of the natural world are being disturbed by changing weather patterns. Climate change, habitat loss, altered fire regimes, and the ever-growing glow of artificial light all pose serious threats to insect populations around the world, and bogong moths are not immune. Their journey has always been difficult; now it is even more unpredictable.
For weather forecasters, this episode is a fascinating reminder that the boundary between technology and nature is more porous than we often assume. The Bureau of Meteorology has been careful to emphasise that the radars are not broken, and that the false rain signals are just something the tools pick up when they encounter unexpected targets. But the incident does highlight some important limitations. With older single-polarisation radar, there is less information to work with, which makes it harder to separate “real” rain from moth swarms, bird migrations, dust clouds, or even drifting smoke. That doesn’t mean the forecast is wrong or that meteorologists are incompetent. It means they constantly have to interpret incomplete data, make educated guesses, and communicate uncertainty to the public. In this case, the Bureau said it could not confirm that every weird echo was caused by bogong moths, because other factors, like temperature inversions, could produce similar effects. That kind of cautious honesty is actually a sign of good science. It acknowledges that the atmosphere is messy, that radars have blind spots, and that human judgment still matters alongside automated systems. Perhaps the bigger lesson is that investing in better technology, such as dual-polarisation radars at more locations, would give forecasters and the public a clearer picture of what is actually happening in the sky. But even with the best equipment, there will always be moments when mother nature throws a curveball. A cloud of moths is not a meteorological crisis, but it is a useful reminder that our weather maps are models of reality, not reality itself. They can show us conditions, but they cannot fully capture every living thing moving through the air.
So the next time you look at your weather app and see rain predicted over your town, but you step outside to find dry pavement and a sky full of stars, pause for a moment before you complain. Look a little closer. Listen to the quiet hum of the evening. Notice the moths fluttering around the streetlight, and think about where they might have come from and where they were trying to go. These are not pests or accidents. They are travellers on a journey that has been repeated for millions of years, one that connects the grasslands of Queensland to the mountain caves of the Alps, and one that links a tiny possum in the high country to the technology we use to forecast the weather on the coast. The radar saw them, even if it didn’t know what they were. We are lucky enough to know a little more, and that knowledge can turn a moment of inconvenience into an invitation to wonder. If you want to help, there are simple things you can do: report bogong moth sightings to researchers, turn off unnecessary lights at night so they aren’t confused, and share what you see with neighbours and friends. There is no need to fear them. They are harmless, gentle insects that are simply following an ancient call. The false rain on the radar is not a mistake to be erased. It is a glimpse of a hidden world, a reminder that even in the middle of a busy human landscape, the sky is full of stories. Some of them look like rain, but they are actually wings.