Noctilucent clouds over Bergen, Norway on June 17, 2020
© Arnim Berhorst
Noctilucent clouds over Bergen, Norway on June 17, 2020
Night is supposed to be dark. But not last night. Across northern and central Europe on June 16-17, the sky lit up with electric-blue ripples from noctilucent (night-shining) clouds. "It was a very bright display," reports Arnim Berhorst, who sends this picture from Bergen, Norway.

"The noctilucent clouds (NLCs) were so widespread, I had to assemble 12 images to capture the complete panorama," says Berhorst. Similar displays were recorded as far south as Germany, Poland, and Switzerland.

NLCs are Earth's highest clouds. Seeded by meteoroids, they float at the edge of space 83 km above the ground. The clouds form when summertime wisps of water vapor rise up to the mesosphere, allowing water to crystallize around specks of meteor smoke.

Last summer, NLCs spread as far south as Los Angeles and Las Vegas, setting records for low-latitude sightings. 2020 is shaping up to be just as good. Record-cold temperatures in the mesosphere are boosting the production of NLCs, pushing them farther south with each passing night. Stay tuned!