Noctilucent clouds, Earth's highest clouds, shine blue in the twilight sky from late May to August in the northern hemisphere ...

Noctilucent clouds usually form close to the poles, but in recent decades, they’re being spotted closer to the Equator ...

The best time to see noctilucent clouds is on clear nights between late May and mid-August, about 90 to 120 minutes after ...

The fleeting glow of noctilucent clouds is once again making its appearance in Earth’s upper atmosphere, signaling the start ...

Cappucci went on: "Because the sun is near the horizon—it's sunset—it's beneath the cloud. That means the cloud ... sun and casts a shadow across the sky." Cappucci also said the dark band ...

which began more than an hour after sunset. It was certainly due to cirrus or a higher kind of cloud, because (1) parts of the illuminated sky stretched in long streaks southwards, and the glow ...

ABOUT sunset on the evening of Sunday ... which I will briefly describe. Two large clouds, covering a considerable portion of the western sky, and separated by an interval leading generally ...