nacreous cloud

That little display had better not stop my nacreous clouds forming this evening or there'll be big trouble.'

Nacreous clouds, typically, are visible in September.

Quilan had missed the nacreous clouds.

It was past dawn, the sky a blanket of nacreous cloud, the sun a glowing patch of milky brightness.

They were nacreous clouds.

In high latitude regions of the stratosphere, nacreous clouds occasionally found there during the polar winter tend to display quite striking displays of mother-of-pearl colorations.

Nacreous clouds are the most dramatic manifestation of polar stratospheric clouds, but they are rare in the Arctic, northern polar regions are warmer than Antarctica.

Studies have established that the majority of UFO observations are misidentified conventional objects or natural phenomena-most commonly aircraft, balloons, noctilucent clouds, nacreous clouds, or astronomical objects such as meteors or bright planets with a small percentage even being hoaxes.