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MetService has issued heavy rain warnings for Westland, south of Otira, from 9am until 3pm, the headwaters of the Otago lakes and rivers until 11am and and in the ranges of Nelson, west of Motueka, until 6pm today.
For Westland, expect a further 50 to 80mm of rain to accumulate about the ranges on top of what has already fallen, and 30 to 50mm near the coast. Peak rates of 25 to 35 mm/h about the ranges, and thunderstorms were possible.
Another period of heavy rain this area was likely from Monday night into Tuesday, and a watch or warning may be issued closer to the time.
For Otago lakes: a further 15 to 30mm of rain may accumulate within 15km east of the main divide on top of what has already fallen. Thunderstorms possible.
Heavy rain watches were also in place for the headwaters of Canterbury lakes and rivers, Westland from Otira north, Buller, the Tararua Range and Mt Taranaki today.
And strong northeast winds could become severe gales in exposed places in the Canterbury high country from 9am until 1pm.
The high parked over New Zealand had been pushed to the east by a series of fronts that were bringing a lot of rain, MetService meteorologist Alwyn Bakker said.
"We're getting this wash of moisture travelling up the country. So most places are going to be seeing rain or showers, except generally the east."
But it won't cold.
Eastern centres of the South Island were expecting highs 10degC above normal for this time of year, Bakker said.
By 11am today, Christchurch was already recording 24degC and was forecast to reach a high of 25degC. Timaru was set to reach 23degC.
Bakker didn't expect records to be broken, but highs may come close, especially in Kaikōura, set to reach 25degC. The previous record for May was 25.8degC in 1999. Records in the town go back to 1991.
In Christchurch, where records date to 1863, the temperature reached 27degC in 2002. Timaru's May record is 26degC, also in 2002.
Other parts of the country would also be warm - Napier can expect 24degC, about 6degC above normal.
Dunedin was forecast to have a high of 20degC, but it will be cloudy with showers until evening, with cooler southwesterlies developing around midday.
Queenstown and Oamaru were set to reach 19degC but it would be cloudy with showers, while a high of 16degC was forecast Invercargill with cloud and showers also.
- NZ Herald and ODT Online