Weather: Downpours, maybe hail, to hit Auckland, Northland

UPDATE: 11:30am

Police have cleared a serious three-vehicle crash at Mata in Northland, which has left one person in a critical condition, as severe weather hits the country's northern region on Friday.

MetService has issued a severe rain warning for Auckland, Northland and Great Barrier Island, with up to 100mm of rain expected to hit the area on Friday night and into Saturday morning.

Rain-slicked SH1 just south of Whangarei is believed to have contributed to the crash involving a logging truck, an SUV and another vehicle on Friday morning.

Police are asking motorists to avoid the area south of Hewletts Rd. The road has been cleared, but there are significant traffic delays in both directions.

The driver of the SUV, travelling south, spun out following an overtaking manoeuvre, and has hit a vehicle in the northbound lane, police said.

The driver of the northbound vehicle is in a critical condition.

Thunder and rain on Friday could disrupt the British and Irish Lions' training for their first tour match, which will take place in Whangarei on Saturday.

Top of North Island warned of downpours, hail

Southern Northland and northern Auckland are due for a drenching at the beginning of the long weekend, with 90mm of rain expected from Friday night into Saturday.

The area north of Orewa and south of Kawakawa will get the worst of it, but Aucklanders and Coromandel residents are also warned to watch out for downpours.

There's a moderate risk of thunderstorms around the east coast north of Auckland, with the possibility of hail.

It could cause havoc on the roads as holidaymakers try to escape the city and head north, especially with the first game of the British and Irish Lions Tour in Whangarei on Saturday evening.

"If you're driving please slow down, lights on and watch your following distance," NZTA says.