Noctilucent cloud season is upon us in the Northern Hemisphere, and NASA has a citizen science project for noctilucent cloudspotters to get stuck into.

Forming in summer months at altitudes of around 50 miles (80.5 km), noctilucent clouds are Earth’s highest clouds. They are only visible during twilight hours, when the rest of the sky is dark but the Sun’s rays are still able to reach way up into the mesosphere from behind the curvature of the Earth. They illuminate these otherwise invisible clouds with an electric blue colour. Their noctilucent name means ‘night shining’ in Latin. While noctilucent clouds are typically seen in latitudes closer to the Poles, they have in recent years been spotted more and more frequently from lower latitudes.

In their Space Cloud Watch project, NASA are inviting members of the public to share their observations and photographs of noctilucent clouds. They are also interested in reports of nights when they have not been observed. The aim is to create a global map of noctilucent cloud sightings, with the purpose of gaining a greater understanding of why these extreme-altitude ice-crystal clouds have been seen over increasing regions of the world in locations farther from the Poles.

Find out more on the Project summary page.

Check out the supporting field guide for observing noctilucent clouds.

Contribute your observations on the Space Cloud Watch website.

Image: Noctilucent clouds over Sumirago, Varese, Italy by Paolo Bardelli