A car and trailer has rolled on State Highway 1 north of Wellington.
The accident was reported north of Churton Park just after 12:10pm.
The incident had been cleared by 1.30pm, but motorists heading north could still expect some delays.
No-one was believed to be injured.
Wellington commuters have already had a wet and miserable morning after two crashes on State Highway 1, and problems with the rail network.
The first accident happened at 6:15am when a car heading into Wellington spun out just south of the Ngauranga Gorge interchange.
The female driver was treated at the scene by Wellington Free Ambulance staff.
While the accident scene was cleared, flow-on delays slowed traffic for hours.
A police car got a flat battery at the scene and needed a jump start from another patrol car.
A second accident happened on the Mana Esplanade at 7:05am when a car went off State Highway 1 and through a fence.
No injuries were reported.
Adding to the delays, a four-wheel-drive vehicle ran out of petrol on the on-ramp to State Highway 1 near Tawa, and was blocking the left lane.
A police communications spokesman said motorists needed to drive to the condition.
''You can't drive at 100 kilometres an hour when it's raining and there's surface water.''
Drivers also needed to increase their following distances in the wet, he said.
Tranz Metro reported delays this morning, due to signal faults and ''operational reasons''.
The affected lines were Wairarapa and Hutt Valley.
- The Dominion Post