The Belfast venue was already sodden, but a deluge from lunchtime yesterday saw large swathes of water around the pitch.
The rearranged game is now likely to be played on one of the free Friday dates on March 7 or 14. There had been a chance that with the Scarlets already in Belfast from Thursday and everything in place, that the game would be played last night. However, with more heavy showers forecast, it was decided that the game was put back until next month.
A decision to postpone the game was made around 4.15pm, following a pitch inspection by referee Leighton Hodges in tandem with officials from both camps.
The referee said: “Large parts of the pitch were under water and the safety of the players would be affected if we went ahead with the game. The safety of the players is paramount and there was no choice but to call off the game.”
Ravenhill is usually able to deal with the inclement weather although Ulster’s clash with Munster was postponed due to snow in 2008.