Chepstow's meeting on Thursday, due to feature the Coral Welsh National, has been abandoned and rescheduled for January 5.
Clerk of the course Keith Ottesen called a 12 noon inspection on Christmas Eve and with further rain forecast, he was left with little option but to call off the meeting.
However, the fixture, which was due to feature the Coral-sponsored marathon, will now be run on Saturday week.
Ottesen said: "We needed some periods of dry weather between the rain. It didn't rain yesterday, but we still wouldn't have been fit to race.
"The Welsh National is one of the most testing races of the year and we have to make sure it is fair and safe to the horses, which it wouldn't have been."
He added: "We have rescheduled for January 5 and the Finale Hurdle will now be worth an extra £5,500 as the value was due to move up from 2012 to 2013.
"All the details about entries for the Welsh National will be available as soon as possible."
The abandonment of Wednesday's original slot means this year's renewal of the Welsh National, which has been sponsored by Coral since 1973, will be televised by Channel 4 and not the BBC.
Coral spokesman Simon Clare said: "With the meeting clearly under threat, Chepstow and Coral have been working closely, and communicating with the vital people at Channel 4, the Levy Board and the BHA, to make sure that the race meeting would go ahead on the first Saturday in January.
"This is a landmark year for the sponsorship, the 40th, and we were all totally committed to getting it on.
"It is desperately disappointing for all the people who work on BBC Racing as they have been great supporters of the Coral Welsh National over the years, but on the other hand it is very exciting that the big race will hopefully feature on the first Saturday of the 'new' Channel 4 Racing presentation.
"It is also the type of race that works brilliantly as a feature handicap on a Saturday, with plenty of popular staying chasers running that have big followings amongst racing fans and punters, and it wouldn't surprise me if the move to a Saturday sees a big uplift in betting turnover on the race.
"With the race being re-opened to all horses that were left in at the weights publication stage, all ante post bets placed since that date are now 'alive' and we are very hopeful of a full field for the Coral Welsh National on January 5."