New Zealand's summer is turning wet and stormy again, with much of the country in for downpours and, from Marlborough north, at risk of thunderstorms.
Parts of Marlborough have already had a drenching and MetService is warning of more downpours in Nelson and Marlborough, Taranaki, parts of Bay of Plenty and the central North Island high country.
Thunderstorms are likely over the northwestern half of the North Island, and northwest Nelson and from Taranaki to western Coromandel Peninsula northwards.
The forecaster said a very humid northerly flow was being pushed ahead of a low pressure system that was expected to move across the country today and Tuesday.
In Nelson, Marlborough and Taranaki, 100-180mm of rain was likely in a 12-15 hour period. Holidaymakers were being warned not to camp near rivers and streams, which could rise rapidly overnight.
Further south the rain is bringing relief for North Canterbury farmers battling the drought. The MetService said most of the the region had had between 10-20mm of rain over the last few days.
A short period of intense rain, with possible thunderstorms, was expected at western Bay of Plenty and Rotorua, with 50-80mm likely over a 4-6 hour period.
Emergency management staff in the Nelson region are warning residents and visitors to brace themselves for a downpour today, with 100-150mm likely to accumulate in the ranges around the city to 3am Tuesday, while 70-90mm was likely in lower lying areas.
Maximum rainfall intensities of 25-35mm an hour are forecast from this evening in isolated thunderstorms around the region.
Nelson Tasman Civil Defence and Emergency Management spokesperson Paul Shattock warned rivers and streams were likely to rise rapidly, and people camping near waterways had to be on guard.
"A major concern that we do have is anyone ... (such as freedom campers) who may be parked up beside the river... might get a bit of a shock if they're not aware." Mr Shattock said Nelson city itself would also "probably cop some" and the worst dump of rain was expected late tonight.
Police in Whangarei are warning motorists to take extra care in wet weather after two serious crashes south of the city in the past week.
A vehicle lost control on State Highway 1 at Smeatons Hill this morning and collided with a northbound car leaving both drivers with moderate injuries.
A police spokesperson said oil and diesel rose to the surface on hot days, so when mixed with rain water the roads became very slippery.
Last week a 45-year-old died when his vehicle crossed the centre line and collided with a logging truck in the same area.
Airlines move to clear backlog due to fog
In Wellington, flights in and out of the city resumed this morning after fog caused massive disruption yesterday.
Jetstar said it expected to clear the backlog from fog delays at Wellington airport by tomorrow afternoon.
Jetstar spokesperson Phil Boeyen said about 1300 passengers were affected, with eight flights cancelled and one international flight diverted to Auckland.
He said normal services resumed this morning, with three additional flights put on to help clear the backlog.
Air New Zealand estimates about 60 flights and almost 3000 passengers were affected.
But it said there was no way of knowing the size of the backlog because many customers had requested refunds, taken credit or rebooked flights.
MetService said fog on Wellington's south coast could affect the airport brieftly but a north easterly wind expected later this evening, should push it out to sea.