Earth's highest, coldest, rarest clouds are back. How to see the eerie 'noctilucent clouds' this summer.

In June and July, turn your head to the north as the stars come out for a chance to observe the extremely uncommon noctilucent clouds, often known as "night-shining" clouds.

Over the next several months, look up an hour or two after sunset and before sunrise to observe ethereal blue, silver, or golden streaks in the northern sky of the Northern Hemisphere.

According to a 2018 study of the phenomena, these strange-looking patterns in the sky are known as noctilucent clouds (abbreviated NLCs), which means "night-shining" clouds in Latin.

About 47 to 53 miles (76 to 85 kilometers) above Earth's surface, in the mesosphere, a region of the atmosphere above the stratosphere and under the thermosphere, are these shimmering, night-shining clouds. NLCs, often called "space clouds," are thought to develop around 62 miles (100 km) above the surface of the planet, just below the invisible line that separates Earth's atmosphere from space.

NLCs develop when water vapor condenses into ice crystals that stick to meteor debris and dust high in the sky, reflecting sunlight. According to Windy, the best time to observe NLCs from the Northern Hemisphere is late June through the end of July, around the time of the summer solstice, when they are easiest to see from 50 to 70 degrees north latitude. However, according to, some NLCs have already been seen this month in colder, northern locales like Denmark.

The Washington Post reports that last summer saw a 15-year peak in NLC sightings. According to NOAA, sightings have risen recently particularly at lower latitudes, presumably because climate change causes more water vapor to be produced in the atmosphere due to an increase in atmospheric methane.

You'll need a clear view low to the northern horizon as the stars start to come out in the late twilight hours if you want to have the best chance of seeing several NLCs in the evening. According to Sky & Telescope, displays are often visible in the lower 20 to 25 degrees of the northern sky. The best method to see noctilucent clouds is with your naked eye, but using the best stargazing binoculars will give you an incredible up-close glimpse of one of the summer's most elusive and magnificent sky views.