This week, reports started ramping up about eerie electric-blue clouds shimmering in nighttime skies in high-latitude regions. The stunning outburst of noctilucent, or night-shining, clouds hails the start of viewing season for these glowing, hypnotically dancing swirls.

The eye-catching wisps show up every year around local summer, and in the Northern Hemisphere sky-watchers can catch a glimpse of them painting the skies from now through August. Viewers in the Southern Hemisphere, meanwhile, should look for the clouds from November to February.

These mysterious, thin veils of clouds appear to form around Earth’s polar regions in the mesosphere, the highest level of Earth’s atmosphere. At these heights near the edge of space, around 50 miles (80 kilometers) up, temperatures are a bone-chilling