Torrential rain has hit the Limassol-Paphos highway has left torrents of water around the tunnel and its adjacent alternative routes, police warned on Thursday.
Drivers have been urged to exercise caution, keep a safe distance from vehicles ahead and switch on their headlights.
Police also advised motorists to obey traffic regulations and road signs to reduce the risk of collisions.
Earlier on Thursday, police had reported no problems on other sections of the main road network.