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Double cloud shadow and rays imaged by Tom Byron in Georgia USA on 4th August '06. Tall cumulus clouds often have rays apparently coming from a dark shadow in the sky. Contrary to intuition, the shadow is below the cloud tops and formed in a lower layer of thin cloud or haze ~ see the explanation below ↓ . ©Tom Byron, shown with permission.

Cloud shadows in the air and on haze layers. The cloud casts its shadow more strongly onto lower layers of haze or cloud which then appear dark to an observer beneath them. The sun's rays (yellow) always shine downwards. The top edge of the cloud is in direction "c". The top of the shadow on the uppermost layer is in direction "b" which to the 'eye' looks higher in the sky than the cloud top. The diagram at left shows the appearance from the 'eye'. A shadow is also cast onto the lower haze level and the edge of this is in direction "a" which appears to be even higher in the sky. The crepuscular rays appear, by perspective, to fan out from the position of the sun but in fact they are all parallel irregularities at the edges of the cloud's shadow tube.