Keep an eye out for rare electric-blue noctilucent clouds in the northern sky

It’s that time of year again, when skywatchers get the chance to see a rare, shimmering type of cloud in the evening sky.

Sightings reported from several provinces, including Alberta, Saskatchewan, Manitoba

This view of noctilucent clouds is seen on June 16 in southern Alberta. The display lasted until dawn, according to photographer Alan Dyer. (Submitted by Alan Dyer/

It's that time of year again, when skywatchers get the chance to see a rare, shimmering type of cloud in the evening sky.

Noctilucent clouds (NLCs), or polar mesospheric clouds, are breathtaking to see. And these are no ordinary clouds. They form in the highest part of our atmosphere, at an altitude of 80 kilometres.

NLCs aren't all that well understood. However, researchers believe they're caused by meteor dust in our upper atmosphere.

They're most prominent in the Northern Hemisphere from roughly June to July (although they can occur from May to August) and need three things to be present: an increase in water vapour, very cold temperatures and particles on which the water vapour can freeze, such as leftover dust from meteors (and sometimes by particles left over from rocket launches).

As well, the sun needs to be at least six degrees below the horizon to illuminate the clouds.

These clouds used to be relegated to the extreme northern latitudes (or southern in the summer months), but over the past decade they seem to be moving south. In 2019, they were seen as far south as California.

Noctilucent clouds seen over the Upper Mission neighbourhood of Kelowna, B.C., on June 16. (Tara Kaman)

A 2018 study suggested they may be moving farther south due to climate change. While NLCs were likely visible for centuries, the authors claim, they were far too faint to see with the naked eye. But as Earth warmed, there was more water vapour present in the atmosphere, allowing them to become brighter. And now with climate change, there's even more water vapour present, particularly at lower latitudes.

Another contributing factor may be the sun. The sun goes through an 11-year cycle, with solar activity — such as sunspots — waxing and waning. The past few cycles, however, have been less active than in the past. When the sun isn't as active, our mesosphere cools down. With increased water vapour and the cooling of the mesosphere, it may make conditions just right for NLCs to form.

As to why they're blue, that's due to ozone. Sunlight that reaches the clouds first passes through the ozone layer, which absorbs red light but allows blue light to pass through.

Noctilucent clouds, as seen from Kaleida, Man., on June 16 at roughly 11 p.m. (Submitted by Sheila Wiwchar)

Over the past week, many people from across the country have seen noctilucent clouds, with many in Alberta, Saskatchewan and Manitoba reporting the wispy clouds shimmering in the sky after sunset.

They've even been seen as far south as Oregon, Washington and Montana, as well as across parts of northern Europe.

But it's not just Earth that experiences NLCs. Just last month, NASA's Curiosity rover photographed the clouds on Mars.

If you'd like to see them for yourself, head out roughly 30 minutes after sunset or before sunrise and look toward the north. The lower your latitude — below 50 degrees north — the more likely they will appear on the horizon, so it's best if you can get somewhere with an unobstructed view. Sometimes NLCs can be confused with cirrus clouds that may be reflecting sunlight. The key difference is that NLCs are wispier and electric-blue. 


Nicole Mortillaro

Senior reporter, science

Based in Toronto, Nicole covers all things science for CBC News. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books. In 2021, she won the Kavli Science Journalism Award from the American Association for the Advancement of Science for a Quirks and Quarks audio special on the history and future of Black people in science. You can send her story ideas at


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