Motorists in and around the Southern Motorway are being urged to find alternative routes or to expect delays this morning as bad weather and crashes cause havoc.

The NZ Transport Agency said there were long queues northbound at the Drury interchange about 9am.

"Consider delaying your journey until congestion eases,'' authorities said.

The advice follows a number of crashes in the Auckland region this morning, as heavy rain and surface flooding - as well as lightning - hammered the city in the early hours.

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Three crashes near Constellation Dr and another near Silverdale, delayed southbound traffic on the Northern Motorway.

A southbound car also broke down on the Southern Motorway's Newmarket Viaduct.