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

Watch this incredible footage of mammatus clouds forming over the sunset. Liz Legge from Indianapolis, USA, captured the rare event as the clouds passed through her neighbourhood. Despite over four ...

DON'T MISS: Weirdest cloud in Canadian history ... which is precisely why the sky is blue. At sunset, however, sunlight travels a much longer distance through the atmosphere.