The annual Birdsville races in outback Queensland are in danger of being washed out after the two-day meeting was postponed and cut back to one day because of an outback drenching.

Roads in and out of the southwest Queensland town have been cut off because of heavy rain over the past 48 hours.

More than 50mm of rain has been recorded in Birdsville over the past two days, making the dirt track unsuitable for racing.

Already the two-day meeting, which was scheduled to be staged on Friday and Saturday, has been condensed into an 11-race program on Sunday.

Racing Queensland spokesman Col Truscott says water has to be drained from the course and a grader is being used to remove the waterlogged top layer of the track to ensure the running of the 134th Birdsville Cup.

He said stewards were overseeing the maintenance work and if the weather improved, as predicted, the meeting would go ahead.

"With favourable weather conditions forecast, the club decided to condense the two days racing into one - creating a super Sunday," he said.

"There are couple of Mt Isa trainers stranded at Bedourie (200km north of Birdsville) and they'll decide on Saturday if they will make the trip."

The revised race meeting will see two races from the 13 originally scheduled abandoned.

Race club vice-president Gary Brook says all roads leading into Birdsville are likely to reopen on Saturday.

The downpour may have caused havoc with race organisers but it's not a disaster for locals.

"The rains have been bittersweet," Mr Brook said.

"While they haven't been great for the races, they have been wonderful for all farmers in the surrounding regions."

Birdsville's population is listed as only 115 but swells to more than 7000 over the popular race weekend.

Mr Brook said the town was still alive with live music, comedy shows, boxing and beer can regattas.