Two breakdowns and a crash at rush hour have caused mayhem on Auckland motorways as the city is hammered by downpours.

City-bound traffic on the Northern Motorway is backed up to Albany after a vehicle broke down in the left southbound lane near the Tristram Rd off-ramp about 7.45am.

Although the vehicle was moved off the road five minutes later, NZTA warned there would still be "significant" delays.

About an hour earlier a truck broke down on the Southern Motorway just before Papakura, blocking the left lane.

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That breakdown was also quickly cleared but motorists travelling north from Drury should expect heavier traffic than normal, NZTA said.

A crash near the Bond St overpass blocked the right lane of the Northwestern Motorway about 6am. It was cleared about 7am but NZTA said city-bound commuters would still face delays.

A section of the Victoria Park Tunnel flooded just before 7am, but has now been cleared.