Overnight rain which flooded fairways and bunkers has forced organisers to reduce the NSW Open at Sydney's Concord course to a 54-hole tournament.

Drenching overnight rain has forced organisers to abandon play on Saturday and reduce the $400,000 NSW Open to a 54-hole tournament - the third successive PGA Tour of Australasia tournament to suffer that fate.

With some fairways at Concord under water after so much rain in recent weeks, there was little choice but officials were confident the course and weather would be fine for Sunday's final round.

It comes after the TPS Sydney tournament at Bonnie Doon had its final round abandoned and the first round of last week's TPS Hunter Valley was also lost to NSW's bad weather.

It means local amateur Harrison Crowe must retain his hot form for just one more round to have a great chance of triumphing over the pros in the NSW Open.

He will go into the final round sharing the lead and playing in the final group with Victorian Blake Collyer, after shooting back-to-back seven-under 64s on Thursday and Friday to reach 14 under.

They are two shots clear of Deyen Lawson, Dimi Papadatos, Jarryd Felton and Jordan Zunic.

Golf NSW chief operating officer Graeme Phillipson said there was no option but to let the course dry out.

"It's disappointing what's happening out there," he said.

"The course generally holds up very well, but we've had so much rain over a long period of time that anything that's falling on the surface is pooling.

"It really needs a good day's drying, and we can make it playable again."

Players have been using preferred lies in closely-mown areas all week because the course was wet from the rains that have swept across Sydney in recent weeks.

Sydney's weather is forecast to improve later today with a maximum temperature of 22 degrees and a southerly breeze, followed by a fine Sunday with a maximum of 25 degrees.