Crepuscular rays (also called "God rays" or "Jacob's ladder") are light beams that appear to fan out from the sun when rays pass through gaps in clouds. They are actually parallel but perspective makes them appear to diverge, like railway tracks.
When to observe
Most spectacular at sunrise or sunset when the sun is low and the atmosphere contains particles (moisture, dust, haze) that scatter light and make the beams visible. Anticrepuscular rays are the continuation of these beams on the opposite side of the sky, where they appear to converge at the antisolar point.