Pastel Iridescent Clouds Over Victoria, and Why They Are Hard to Catch on Camera

Thin clouds over Melbourne turned soft rainbow colors over the weekend. People in Mount Waverley and Caroline Springs, both suburbs of Melbourne, photographed the shifting pastel patches, and the images spread quickly among local observers The Guardian.

Sarah Scully, a senior meteorologist at Australia's Bureau of Meteorology, said iridescent clouds are not uncommon in Australia but are rarely captured The Guardian. They can be present in the sky more often than they appear in photographs.

These clouds often start as cirrus, high thin cloud made of ice crystals. The color forms when sunlight bends and spreads around those tiny crystals, a process called diffraction. The effect is strongest in newly formed cloud where the crystals are still close to the same size, like light passing through a very even sieve. Small patches of cloud also show the color more clearly Bureau of Meteorology.

That light behavior sets iridescence apart from two lookalikes. Rainbows come from both bending (refraction) and reflection of sunlight inside water drops, and they show colors in a fixed order with neater bands. Sun dogs are bright pillars of light on one or both sides of the sun and sit lower toward the horizon than iridescent clouds. Location, shape and color order let a trained observer tell them apart in the field.

Victoria has hosted this before. Juan Rodriguez photographed an iridescent rainbow cloud in Newport, Victoria, and that photo is the January image in the 2026 Australian Weather Calendar Bureau of Meteorology.

The broader context here is the gap between happening and being recorded. Uniform crystal size lasts a short time. The cloud patch must be small, the sun angle must be right, and someone must be looking from the right spot. Most suitable cirrus passes without notice. A weekend over a large city raises the chance that someone looks up with a camera.

In my view, the interest for specialists is less about rarity than about clear naming. Keeping diffraction-based iridescence separate from refraction-plus-reflection rainbows and from lower sun-dog pillars gives forecasters, spotters and reporters a shared vocabulary. Clear labels cut down on misidentification and keep attention on what uniform crystals tell us about a cloud's stage of growth.

Looking at what this means for public weather watching, curation closes the loop. Phone photos from Mount Waverley and Caroline Springs bring speed and volume. The Rodriguez calendar image brings a lasting reference. The public gets practice in telling iridescence from rainbows and sun dogs, and weather offices get more timely, better-described sightings for outreach and training.