Challenging wet conditions have made work difficult for search crews as a major, multi-agency hunt for a woman who fell from a waterfall enters its third day.

The 20-year-old woman was reported missing early on Sunday afternoon following reports she had slipped and fallen at Belmore Falls, in the NSW Southern Highlands region.

Chief Inspector Brendan Bernie, from the Hume police district, told ABC Radio conditions had made it tough to continue the search.

Large parts of NSW were hit with heavy rain over the weekend, with multiple areas receiving more than a month’s in one day.

“It is still slippery, there is a lot of water and dampness around the areas we’re searching,” Bernie said.

“We are confident we can identify the location where she actually has slipped, but unfortunately we haven’t been able to determine (the exact position yet).”

The extensive water- and land-based search has involved local police and specialist rescue officers, as well as ambulance staff, State Emergency Service volunteers and other personnel.

It resumed on Tuesday morning after the operation was suspended on Monday evening due to low light.

Bernie said authorities would be using all available resources in an attempt to find the missing woman.

Police have been talking to a male friend, who was with the woman on Sunday, as they try to work out what happened in the lead-up to the incident.

“The full circumstances around why they were there that day is still to be determined,” Bernie said.

“Unfortunately we haven’t been able to determine where the female has ended up.”

Authorities are also urging the public to be cautious when hiking during wet weather amid suggestions the woman could have been attracted to the falls due to the high volume of water from the rains.

“We ask people to use the necessary precautions to avoid getting hurt,” Bernie said.

– AAP