The New Zealand Transport Agency said SH2 between Waihi and Paeroa was also a possible chokepoint. Other congestion hot spots were SH3 between Otorohanga and Eight-mile Junction, SH1 from Waiouru to Taihape, and SH2 north of Napier.
The agency's Mark Owen said roads would be busy for people heading out of Wellington this evening and tomorrow morning, and back into the city on Monday, with queues on SH1 north of Otaki likely.
In the South Island, police expect heavy traffic and said motorists should prepare for frustrating situations, especially when driving behind slower vehicles.
The Transport Agency expects highways around Kaikoura, Arthur's Pass and Lewis Pass to be busy. SH6 from Nelson to Blenheim and SH1 from Christchurch to Ashburton are also congestion hot spots.
Senior Sergeant Steve Larking said the weekend forecast looked "good enough", but motorists should still drive more slowly and be cautious of frosty mornings and hazards such as black ice, which made roads slippery.
Associate Transport Minister Craig Foss said road users should take extra care.
"Rain, snow and ice can make the road a treacherous place," he said. "Motorcyclists and pedestrians are particularly vulnerable in poor weather."
The official holiday period for Queen's Birthday weekend begins at 4pm today and ends at 6am on Tuesday. Last year's holiday toll was five, from a total 87 reported injury crashes.
WeatherWatch forecasters expect a warmer long weekend after some chilly conditions this week.
"The high pressure currently bringing the cold but settled weather to New Zealand is replaced by a northerly flow this weekend.
The warmest spots will be in the north and the east, with Christchurch forecast to reach the high teens for the Athletics New Zealand Half Marathon Championships being held there on Sunday."
But WeatherWatch warned conditions would be unsettled in many places next week as a zone of low pressure formed over the Tasman Sea before bringing wind and rain to New Zealand.
Warmer weather will come with a price - with wetter weather expected in places.
MetService meteorologist John Law said a high-pressure system should bring northerly or northwesterly winds and an increased chance of rain.
"We're going to find the rain arrives in the South Island as we go through Friday afternoon.
"As we go through in towards Saturday it starts to creep north, and you'll find it starts to turn cloudier on Saturday in Auckland, and once we head through in towards Sunday we'll start to find some spots of late drizzle."
He said that sadly those northerlies would bring some wet weather on Monday.
The change in wind direction - bringing warmer but wet weather with it - would hit the west of the country hardest for Queen's Birthday weekend, Mr Law said.
"If you're heading out towards the east for the long weekend, somewhere like Hawkes Bay, Gisborne or even down towards Canterbury, it looks like better, drier weather, and a little bit warmer as well."
