Police are reminding drivers to take it easy while traffic backs up on Auckland's motorways as holidaymakers flee the city.
A crash on the Western Motorway and a breakdown on the Southern Motorway near Greenlane has also caused congestion.
New Zealand Transport Agency traffic cameras show traffic piling up on the Southern Motorway, particularly between Khyber Pass and St Marks, Mount Wellington and Papakura.
Traffic is crawling at 15km/h between Highbrook and Redoubt Rd at Manukau.
Social media users were warning fellow motorists to avoid Auckland motorways where possible.
NZTA said shortly after 4pm northbound traffic was heavy between Silverdale and Puhoi, and city bound between Esmonde Rd and the Harbour Bridge.
On the Western motorway it was busy between Great North Rd and Lincoln Rd.
There had been crashes on Lincoln Rd and near the Te Atatu Rd offramp on the Western Motorway. The latter had since been cleared.
A breakdown - also now cleared - near Greenlane had also caused delays.
Traffic at Waterview tunnel was flowing lightly, NZTA said.
A police spokesperson said traffic was heavy and asked drivers to take it easy.
"Police would like to take this opportunity to remind drivers to allow lots of time to get to your destination, ensure you keep suitable following distances, wear your safety restraints and make sure you stick to the speed limit."
The slow crawl out of the city comes as Aucklanders have been warned to expect traffic delays on SH1 from midday today as they leave town for Anniversary Weekend.
The NZ Transport Agency says motorists travelling northbound and southbound could face delays and have been advised to check hotspots.
Barney Irvine, Principal Adviser - Infrastructure for the Automobile Association, said the holiday traffic hotspots around the city are the usual suspects:
State Highway 1 north between Puhoi and Wellsford; Southern Motorway around Takanini; SH2 on the way to Coromandel
"We'd expect these hotspots to get pretty busy from 2pm today, and stay that way through until 7 or 8pm. So leaving a bit later tonight – or even tomorrow morning – can really pay off.
"Of course, it's not just this evening – tomorrow and Sunday can also get really heavy for people leaving town. If possible, people should try to avoid driving through the hotspots between 10am and 2pm," he said.
Irvine said getting stuck in holiday traffic is never fun, but soaring temperatures take the stress and discomfort to the next level.
Many drivers will get drowsy because of the heat, so taking regular breaks is extra-important.
People shouldn't underestimate just how quickly the interior of their car heats up when they park up and leave the doors and windows closed in hot weather. That means leaving children and pets inside isn't just uncomfortable, it's dangerous, and we'd advise people to avoid it if they can, Irvine said.
He said Monday signals the end not just of the long weekend but, for many schools, the end of the summer holidays, so we'll see a lot of people coming back to the city. The holiday hotspots typically stay heavy right through the afternoon (midday-6pm), and we'd recommend that motorists avoid driving through them at that time – if they can.
"So our general advice to motorists: don't just jump in your car and go. Plan out your departure time well in advance, and check highway conditions on-line closer to the time. Adjusting your travel times by a couple of hours can save you a really painful start or finish to the holiday," Irvine said.
The Hotspots site shows traffic is expected to be heavy from midday until 7.30pm southbound on SH1 and from noon until 7pm from Puhoi to Wellsford northbound.
Traffic is already heavy around Taupiri on SH1, north of Hamilton, and expected to stay that way until 6pm.