Bogong Moth Swarms Baffle NSW Weather Radars 2026

Bogong moth swarms are bamboozling weather radars across New South Wales, creating false rain signals that have meteorologists scratching their heads. Every night, particularly across eastern NSW and around Sydney, radar imagery shows widespread rain—yet often not a drop reaches the ground. The culprit? Massive numbers of bogong moths on their annual migration to the Australian Alps.

Why Bogong Moths Appear on Weather Radar

Weather radars are designed to detect precipitation by sending out radio pulses that bounce off water particles. But these pulses can also reflect off insect bodies and wings. When billions of bogong moths take flight, they create echoes that look remarkably like light, widespread rain. According to the Bureau of Meteorology, large insect swarms can produce radar echoes similar to drizzle, especially near sunrise and sunset when moths are most active.

This phenomenon isn't new. During the Sydney Olympic Games in 2000, a swarm of bogong moths attracted by stadium lights was so immense that meteorologists mistook it for rain. Now, 26 years later, the moths are back in big numbers—and firmly on the radar.

The Challenge of Confirming Moth Swarms

While it's possible that radars across eastern NSW are detecting bogong moths, a Bureau of Meteorology spokesperson notes that completely attributing the effect to moths is challenging. Other factors, such as temperature inversions, can cause similar radar echoes. Temperature inversions occur when warm air sits above cooler air, bending radar beams and creating false returns. Distinguishing between biological and meteorological targets requires careful analysis.

Dr Kate Umbers, a biologist working to conserve bogong moths, says radar data could be "absolute gold" for scientists. By studying these echoes, researchers can track moth migration patterns, population sizes, and responses to environmental changes. This unconventional data source might fill critical gaps in our understanding of these iconic insects.

Bogong Moth Migration: A Natural Wonder

Bogong moths (Agrotis infusa) are famous for their long-distance migration. Each spring, they travel from breeding grounds in Queensland, New South Wales, and Victoria to cool caves in the Australian Alps, where they aestivate (a summer dormancy) to escape the heat. In autumn, they return to the lowlands to breed. This journey can span over 1,000 kilometers, and the moths navigate using celestial cues, including the moon and stars.

The moths play a vital role in the ecosystem. They are a traditional food source for Aboriginal people and an important prey item for birds, mammals, and reptiles. However, their numbers have declined dramatically in recent years, likely due to drought, habitat loss, and climate change. The current surge in sightings is a welcome sign, but scientists remain cautious.

How Weather Radar Detects Moths vs. Rain

Radar technology distinguishes targets based on reflectivity, velocity, and dual-polarization. Rain droplets are spherical and fall steadily, while insects are irregularly shaped and fly erratically. Modern dual-polarization radars can differentiate between the two by analyzing the shape and orientation of particles. However, dense swarms can still confuse the algorithms.

Key Takeaways

• Bogong moth swarms are creating false rain echoes on NSW weather radars.
• The phenomenon occurs mainly near sunrise and sunset during migration season.
• Radar data could help scientists track moth populations and migration.
• Distinguishing moths from rain requires advanced radar analysis.
• The moths are migrating to the Australian Alps for summer dormancy.

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