Many will be in for a dry start before a series of fronts and troughs carry rain and showers over western parts of the country.
"For the South Island, it's much wetter than most other places ... the west coast of the island we're expecting heavy rain," meteorologist Melissa Oosterwijk said.
"Whereas west areas of the North Island have some isolated showers around but that's not heaps of rain."
The rain will slowly develop over southern areas of the South Island's west coast before sliding, spreading further north during the afternoon.
Patches of rain, mainly showers, might spread over the Southern Alps and on to areas of Canterbury and Otago but later in the day, if at all.
Asked whether the west coast of the North Island would be wet tomorrow, MetService's Oosterwijk said only some parts would.
"It's more of a showery flow in the North Island, it's one of those 'if the showers move on top of you then you'll get wet'," she said.
"But most places will probably be quite alright for most of the day."
Those in the Auckland region can expect a nicer day today, after most areas experienced periods of rain yesterday.
"We are expecting some isolated showers but there should be a period, particularly in the morning and afternoon, where it is mostly dry," Oosterwijk said.
Tomorrow, a trough is forecast to quickly slide eastwards across central and northern parts of New Zealand, bringing periods of heavy rain to many.
There is also low confidence of warning amounts of rain for Westland, Nelson, the Marlborough Sounds, central North Island high country and eastern Bay of Plenty and Northland.
Thursday weather outlook
Whangarei: Cloudy periods. A few showers developing evening. Westerlies tending northerly. High 16C, Overnight 10C.
Auckland: Cloudy periods. Chance early showers, then further showers developing evening as westerlies tend northerly. 15C, 10C.
Tauranga: Partly cloudy. One or two evening showers. Westerlies tending northerly. 15C, 9C.
Hamilton: Cloudy periods with a few showers. Westerlies tending northerly. 14C, 7C.
Napier: Fine, with high cloud from afternoon. Northwesterlies tending northeasterly late. 16C, 6C.
New Plymouth: Cloudy periods with a few showers, more frequent from evening. Westerlies turning northerly. 15C, 10C.
Wellington: Becoming fine early as winds turn northerly. Cloud increasing and a few showers developing towards evening. 13C, 10C.
Nelson: Fine and frosty, with increasing high cloud. Rain developing evening. Northerlies developing in the evening. 12C, 6C.
Christchurch: Fine and frosty, with increasing high cloud. Chance evening shower. Northeasterlies developing afternoon. 12C, 5C.
Queenstown: Fine at first, then cloudy with a few spots of rain from afternoon. Northerlies, dying out overnight. 10C, 1C.
Dunedin: Fine at first, then cloudy with a few spots of evening rain possible. Northerly breezes. 11C, 5C.
Invercargill: Fine and frosty, then cloudy with a few spots of rain from afternoon. Northerly breezes. 10C, 3C.