The downpour, which began shortly before match was due to kick off at 1700 local time (1600GMT), left the pitch at the Estadio de Bata in Equatorial Guinea severely waterlogged and caused flooding in the players' tunnel.
Match officials spent a number of minutes inspecting the playing surface before returning to their dressing room to discuss whether the match could go ahead.
Eurosport later said a decision would be taken at around 1750 local time.
The Estadio de Bata is also due to host the second Group A encounter between co-hosts Equatorial Guinea and Senegal at 2000 local time.
The delay coincided with an improvement in the weather conditions, and at around 1745 tournament officials confirmed that the match would kick off at 1815 local time.