Police are urging motorists in NSW to slow down and drive cautiously in the wet weather following 127 major crashes on Saturday.

The weather is expected to deteriorate further on Monday as ex-tropical cyclone Oswald tracks south from Queensland.

NSW Police said on Sunday that officers on the first day of the long weekend on Saturday attended 127 major crashes in which 46 people suffered injuries, but fortunately there were no deaths.

More than 800 motorists were detected speeding and issued with speeding infringement notices, while more than 42,000 breath tests of drivers resulted in 47 people being charged with driving under the influence of alcohol.

Double demerits points are being enforced for speeding, seatbelt/restraint and helmet offences until the end of Monday.

Acting Superintendent Mark Cook, Traffic and Highway Patrol Command, said motorists needed to maintain focus on the roads in the weather conditions.

"We are asking motorists to take extra caution when driving and ensure they are well rested before starting out on their trip."

Acting Supt Cook urged drivers to consider delaying their travel plans until conditions improve.