The organisers of the RaboDirect PRO12 will confirm the new date for Ulster v Scarlets in the coming days.
"It's very unfortunate - we don't remember a match being postponed by rain this last 30 or 40 years," said Ulster Rugby Chief Executive Shane Logan.
"There's been weeks of heavy rain. The match was probably playable at lunchtime but with no respite the referee had no choice but to call it off.
"We hope it be played on March 14, as there's a gap in the programme for that date."
Tickets for tonight's game in Belfast will be valid for the rearranged fixture.
Ulster Rugby would like to thank the fans for their understanding in these exceptional circumstances and to apologise for any inconvenience caused.