All three of the synoptic Gospels report that when Jesus was crucified, the sky became dark in the daytime from noon to 3 PM, when Jesus died at the time of the evening sacrifice in the Temple. But there is no known plausible natural cause for the crucifixion darkness.
Not a Solar Eclipse A solar eclipse could not have occurred on or near the Passover (Full Moon), when Jesus was crucified. Solar eclipses only occur when the Moon is "New" and can occur only approximately two weeks before or after a Full Moon. In addition, solar eclipses are much too short to account for three hours of darkness. The maximum possible duration of a total solar eclipse is seven minutes and 31.1 seconds. The only total eclipse visible in Jerusalem in this era occurred late in the year 29 AD on 24 November at 11:05 AM and lasted for just one minute and forty-nine seconds.
Not Any Other Natural Cause People have unsucessfully attempted to explain the crucifixion darkness in terms of sunstorms, heavy cloud cover, the aftermath of a volcanic eruption, etc. But no one has yet found a plausible natural cause.