The bleak end to spring continues with more overnight snow in the south and cold showers spreading across New Zealand.

MetService meteorologist Karl Loots said while much of the country would see some rain, today the major weather story was on the South Island's lower east coast.

About 35-55mm of rain had fallen in the past 12 hours from South Canterbury to Southland, with up to 120mm expected in places by 9pm tonight.

"It is quite a dry part of the country, so while in other areas it wouldn't cause floods I wouldn't be surprised if there was flooding in some of those areas today," Loots said.

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The North Island wouldn't be escaping the wet today either, with isolated showers from Northland to Wellington becoming more frequent through the morning.

These would spread east late morning and through the day with an unstable northwesterly flow accompanied by potential thunderstorms, with periods of heavy rain and a chance of hail.

Auckland was in for a high of 16C, with showers developing this morning, possibly heavy, with hail and thunderstorms until the early evening.

The wet weather in the far south was being driven by a slow moving system that had been over the country the past two days, driving in moisture from very far north of New Zealand. The same system was behind heavy snowfall in places, with up to 40cm falling to 700m yesterday.

Another 20cm was forecast in parts of Central Otago and Southern Lakes above 700m today, with lesser amounts to 400m.

Loots said most of the snow had fallen overnight, and the snow level was rising from here.

Road snow warnings were in place today for the Desert Road (State Highway 1), Lewis Pass (SH7), Arthur's Pass (SH73), Porters Pass (SH73), Lindis Pass (SH8), Crown Range Rd and Milford Rd (SH94).

Rain would start easing from tonight in the South Island, with showers increasing in the North Island into Wednesday. The South Island was in for another hit of rain on Wednesday night.

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There would be some brief respite Thursday as the system moved away to the east, before another system approached from the Tasman Sea on Friday and Saturday, delivering further unsettled weather across the country.

Today's weather

Whangārei

Showers, possibly heavy with hail and thunderstorms from late morning, clearing evening. Westerlies. 17C high, 9C overnight.

Auckland

​ Showers developing morning, possibly heavy with hail and thunderstorms until early evening. Westerlies. 16C high, 10C overnight.

Hamilton

Showers developing morning, possibly heavy with hail and thunderstorms, clearing evening. Light winds. 16C high, 6C overnight.

Tauranga

Fine at first. Showers afternoon and evening, possibly heavy with hail and thunderstorms. Northwest breezes. 17C high, 8C overnight.

New Plymouth Showers, chance heavy with thunder, hail late morning and afternoon. Northerlies. 15C high, 8C overnight.

Napier Mainly fine, chance of a shower from afternoon. Northeasterlies. 18C high, 8C overnight.

Whanganui​ Cloudy periods. Showers in the afternoon and evening, chance thunder and hail. Light winds. 18C high, 7C overnight.

Wellington Fine spells after morning showers. Southerly breezes. 14C high, 8C overnight.

Nelson Fine spells. A few showers from late morning, chance hail from afternoon. Light winds. 15C high, 8C overnight.

Christchurch Showers easing in the morning. Rain from afternoon with heavy falls, easing by evening. Cold southwesterlies, but northeast from evening. 12C high, 4C overnight.

Dunedin Rain, heavy at times, gradually easing. Cold southerlies, strong at times, then northerlies at night. 14C high, 8C overnight.