Imagine waking up in the middle of a bright, golden spring morning in southeastern Australia. The sun is pouring through the windows, the sky is a flawless blue, and yet your phone is buzzing with a weather alert that says light rain is on the way. You step outside, squint at the emptiness above, and wonder if the Bureau of Meteorology has finally lost its collective mind. As it turns out, the forecast isn’t necessarily wrong in the way you think—but the rain isn’t rain at all. The real culprits are tiny, winged travelers: Bogong moths. In one of the most charming and unexpected quirks of weather science, enormous swarms of these migrating moths are flying just below the Bureau’s radar beams, and the radar is reading their soft, fluttering bodies as precipitation. It’s an odd explanation for a very human moment of confusion, but it’s also a beautiful reminder that the natural world is always moving around us, sometimes in ways that scramble our technology and remind us that we are not quite as in control of our information as we like to believe.
The phenomenon all comes down to the annual migration of the Bogong moth, a species with its own remarkable story. Every year, these moths undertake a long journey from their breeding grounds to the cooler, higher country of the Australian Alps, where they gather in enormous numbers among the granite boulders and caves. For years, scientists and conservationists watched their populations with concern, but this season something wonderful has happened: the numbers have surged. According to Dr Marissa Parrott, senior conservation biologist at Zoos Victoria, sightings of the curious insect are running at about six times higher than in previous seasons. She described the boom as a cause for real joy, saying, “It’s just wonderful to see the numbers coming back to where they should be and everyone enjoying a visit from an endangered species.” That’s right—these unassuming moths are officially listed as endangered, and their sudden abundance is being celebrated by researchers and nature lovers alike. The public has thrown itself into the effort to track them too, with the Zoos Victoria Moth Tracker website already recording more than 12,000 verified sightings from citizen scientists across the region. What started as a few confused forecasts has turned into a genuine community celebration of a migration that most people had never even heard of.
The Bureau of Meteorology, for its part, has been remarkably graceful about being fooled by a bunch of moths. A spokesperson told 7NEWS.com.au that it is indeed possible that radars across eastern New South Wales are detecting Bogong moths, though they carefully added that they could not completely confirm that all the unusual signals were entirely due to them. Crucially, the Bureau emphasized that its radars are not malfunctioning. Radar technology, by its very nature, picks up all sorts of things in the atmosphere, not just precipitation. “Radar technology can pick up ‘echoes’ from non-meteorological matter such as buildings, birds and insects,” the spokesperson explained. When large numbers of insects are on the move, they can produce a signal that looks very much like light, widespread rain—especially around sunrise and sunset, when the atmosphere is calm and the radar beam is more likely to capture low-flying creatures. The Bureau confirmed that there have been increased echoes displaying on radars across eastern NSW that are definitely not precipitation, and they suggested that other atmospheric quirks, such as temperature inversions, could also be playing a part in the phantom rain. It’s a reminder that even our most advanced forecasting tools are still at the mercy of the living, breathing, flying world they are trying to observe.
To understand how a moth can disguise itself as rain, it helps to know a little about how weather radar actually works. The Bureau’s radar dishes rotate constantly, sending out short pulses of electromagnetic waves in every direction. When those pulses hit water particles in the atmosphere, they bounce back to the dish like echoes bouncing off the walls of a cave. The time it takes for the signal to return tells meteorologists how far away the precipitation is, and the strength of the return tells them how heavy it is. That information is then translated into the familiar colorful maps we see on our phones and television screens. But here’s the catch: radar waves do not have a personality. They simply bounce off things—and many of those things are not raindrops. An insect, a bird, a bunch of dust, or even a building can scatter the signal in a way that looks remarkably similar to precipitation. Older radar dishes, in particular, cannot easily tell the difference between a speck of water and a speck of moth. As the Bureau noted, some of the more modern radars in New South Wales, such as those at Terrey Hills and Yeoval, are equipped with dual-polarisation capability, meaning they send and receive both horizontal and vertical waves. This allows them to work out the shape and size of whatever is in the sky, and to filter out the echoes that are clearly coming from insects rather than rain. But older single-polarisation radars, like those at Wollongong and Newcastle, simply lack that filtering ability. So there they sit, faithfully reporting a drizzle that has no intention of ever wetting anyone’s hair.
For anyone living in the affected areas, this has created a somewhat surreal daily routine. The forecast says “possible light showers” or “patchy rain,” so you grab an umbrella, maybe throw on a waterproof jacket, and then step outside into sunshine so warm you immediately wonder whether you’ve been tricked. Some people might glance back at their phones, convinced they’ve misread the forecast. Others might just mutter about unreliable weather apps and move on with their day. But the truth is far more delightful than a software glitch. Right now, millions of Bogong moths are pouring through the skies of eastern New South Wales, and their migration could continue for up to a few months. During that time, the region’s weather maps may keep showing ghost rain that has everything to do with the natural world and nothing to do with meteorology. The Bureau has even offered some practical advice for the confused and the damp-looking: before you leave the house dressed for rain, take a quick peek upward. If you see a sky full of tiny, fluttering shapes, you can safely leave the umbrella at home. In other words, the answer to “is it really going to rain?” might just be “no, that’s moths”—and that is a much better story than a routine weather forecast anyway.
There is something quietly beautiful about this whole episode. It is a collision between ancient seasonal rhythms and modern satellite-age technology, and the technology has not come out looking particularly smart. For all our satellites, supercomputers, and radar networks, a small endangered moth has managed to make fools of us on national television. And yet, it feels less like a failure and more like a wake-up call—a gentle nudge to remember that our maps of the world are not the world itself. The data we rely on is a translation of messy, living, constantly moving reality, and sometimes the translators get a little confused. The Bogong moths are not trying to trick anybody; they are just doing what they have always done, following an ancient migration path through the mountains, gathering in the cool crevices of granite caves, and carrying on a life cycle that has been unfolding for millions of years. The fact that their journey happens to coincide with our radar beams is a reminder that we share this landscape with creatures far older than our technology, and that even our most sophisticated instruments cannot fully separate the weather from the birds, the insects, and the beating heart of the natural world. So the next time your phone tells you it’s raining while the sun is blazing, don’t be annoyed. Look up, smile, and thank the moths for making your day a little more magical.