The heavy rain would move and spread through the North Island, MetService meteorologist Tom Adams said.
"The front will stall in the upper North Island," he said.
Areas such as the Bay of Plenty, Waikato and further north may get heavy rain over the long weekend, Mr Adams said.
Weather for the long weekend in Auckland was currently forecasted to see rain on Saturday, but that would ease to showers on Sunday.
WeatherWatch reported the front would be "very slow moving" on Saturday.
North of Lake Taupo may be cloudy and wet on Saturday, with conditions easing later in the day or in the evening as a southerly change moves in.
Showers would improve by Monday with lighter winds for many North Island areas.
The weekend weather for the South Island would be off to a better start with fine spells in Christchurch and Nelson.
But there would be a "wee bit of a front bringing rain to Fiordland and Southland".
Mr Adams said there was still a lot of uncertainty and advised people to regularly check for updates on the MetService website.
The official holiday road period runs from 4pm on Friday, to 6am on Tuesday.
Police would be out in force on the roads over Labour Weekend, officer in charge of the Waikato Highway Patrol, Senior Sergeant Steve Ambler said.
"As part of this our approach this weekend officers will be out in numbers and highly visible on Waikato roads over the long weekend. But we can't do it alone and the public can play a key part alongside us," he said.
"And that part is reporting bad driving behaviour."
There had been an increase in the public reporting bad driving on the roads, he said, with figures showing the number of driver complaints jumped risen to 1413 in the June to September period this year, from 1252 in the same period last year.
"This increase indicates to us that the motoring public's tolerance for anti-social behaviour on our roads is reducing and we want to tap into this to prevent trauma on our roads," Mr Ambler said.
He urged people to call *555 if they say bad behaviour on the roads.
New Zealand Transport Agency (NZTA) safety director Ernst Zollner advised those planning a trip away for the long weekend to drive at a safe speed.
"Don't think of the speed limit as a target to aim for, instead drive at a speed that is safe for the type of road, the weather conditions and the number of vehicles on the road," he said.
"Think of the time getting to your destination as part of your 'weekend away', make the most of being together with friends or family even if it is in the car, relax and enjoy your journey, that way everyone's more likely to arrive safely."
The NZTA also advised drivers to plan ahead to avoid congestion hot spots.
"We know that traffic is heaviest heading north on State Highway 1 between Puhoi and Kawakawa from mid-afternoon on Friday and again on Saturday morning, and then returning south again from 10am on Monday morning.
"It's also busy heading south out of Auckland on SH1 from midday on Friday until around 8pm, and then again on Saturday from about 9am, and picks up again heading north to Auckland from lunchtime on Monday through until 7pm," he said.
The holiday road toll for Labour Weekend last year was three with 78 injury crashes, according to Ministry of Transport figures. The three deaths included a driver, passenger and pedestrian.
The most common reason for a crash over Labour Weekend last year was losing control, which made up 48 per cent of crashes. This was followed by travelling too fast for conditions, at 35 per cent, alcohol at 20 per cent, inattention also at 20 per cent, and failing to give way or stop at 15 per cent.
About 60 per cent of the injuries occurred on the open road.
Congestion hot spots:
• Auckland
- SH1 Takanini
South on Friday October 23 - 12.30pm to 8pm
South on Saturday October 24 - 9am to 2.30pm, with the heaviest period expected to be 9:30am to 11am.
North on Monday October 26 - 12pm to 7pm, with the heaviest period expected to be 1.30pm to 6pm.
• Wellington
- SH1 Waikanae
North Friday October 23 - 9.30am to 7.30pm, with the heaviest period expected to be 1.30pm to 7pm.
North on Saturday October 24 - 9am to 2.30pm, with the heaviest period expected to be 10.30am to 12pm.
South on Monday October 26 - 11.30am to 8pm, with the heaviest period expected to be 2pm to 6.30pm.
• Christchurch
- SH1 between Christchurch and Kaiapoi
North Friday October 23 - 1.30pm to 7pm, with the heaviest period expected to be 2.30pm to 5.30pm.
South on Monday October 26 - 1.30pm to 5pm.
