Wellington, currently overcast, and its surrounds had the chance of a "really heavy downpour" at times today but the situation was volatile, and revellers should keep their fingers crossed for clear skies at midnight.
"So yes, some places will be 'washed out' but apart from a few downpours we're hoping many regions will still be fairly dry tonight," WeatherWatch said.
This afternoon, Timaru was the hottest spot in the country, reaching 26.9C, according to MetService.
Westport was the wettest, and Nelson the windiest.
A severe weather watch was in place for Canterbury, Otago, Buller, Taranaki, Nelson, Marlborough and Wellington this afternoon.
"A series of fronts are expected to move over southern and central New Zealand today," MetService said.
Heavy rain and strong northerlies were expected to accompany these fronts.
A heavy rain warning was in force for the ranges of northern Fiordland, Westland, northwest Nelson and the Canterbury headwaters between Aoraki/Mt Cook and Arthur's Pass.
Patchy conditions were in store for many of the country's favourite New Year holiday locations tonight but for most, clearer skies were expected as New Year's Day progressed.
HOLIDAY HOTSPOTS
Kerikeri: Rain is expected to continue for the rest of the day but MetService said occasional rain should clear late tomorrow morning.
Coromandel Peninsula: Occasional rain was likely to develop in Whitianga this evening. Similar showers were expected across much of the peninsula this evening and tomorrow.
Gisborne: There should be clear skies in Gisborne at the stroke of midnight but MetService predicted a chance of high cloud and a "few spots" of rain this evening. The area could experience some light showers tomorrow morning but clear skies should return tomorrow afternoon.
Mt Maunganui: Rain is expected tonight and early tomorrow morning but should clear before midday tomorrow.
Nelson: Rain is expected to clear by about 10pm tonight but a coastal gale warning is in place for boaties until midnight tomorrow. The MetService forecasts sunny skies for the city tomorrow.