New Zealand is "stuck" in a humid flow bringing warm temperatures to much of the North Island but scattered rain throughout the country.
A low pressure system in the Tasman Sea and a high pressure system to the east is trapping a moist, northeast flow over the country.
"The upshot of that is the country is stuck in the northeast flow, dragging humid air down," Metservice forecaster Matthew Ford said.
Much of the country will be under clouds, with scattered showers and northeast winds today.
Temperatures will reach the mid-20s across most of the North Island, but the South Island will struggle to get above the late teens. Some areas will reach the early 20s.
"The rain has not been particularly heavy, but it has been ticking over in places," Ford said.
"Upper parts of the South Island, including Buller and Westland will have occasional rain most of today. In a lot of places the rain will pull away this afternoon, including Marlborough and Canterbury, and rain over the lower North Island will ease this morning.
"Places more exposed to the northeasterlies, including Auckland, will be stuck with showers for most of the day."
The same weather system is expected to stay around for the rest of the week.
"It will be a bit of a mixed bag for the rest of the week, as the humid northeast flow persists over the country," Ford said.
"There will be a bit of a change in the South Island over the weekend, as a northwest flow comes through, but the North Island will stay much the same."
Cloud increasing and a few showers from afternoon. Easterlies. 26C high, 20C overnight.
Auckland: Humid and often cloudy with a few showers. Northeasterlies. 25C high, 19C overnight.
Hamilton: Mainly fine, but some morning drizzle. Light winds. 24C high, 16C overnight.
Tauranga: Fine breaks. Chance afternoon shower. Light winds. 23C high, 20C overnight.
New Plymouth: Morning cloud with chance shower, then fine. Northeasterly breezes. 25C high, 17C overnight.
Napier: Fine, with high cloud. Light winds. 24C high, 16C overnight.
Wellington: Rain gradually clearing during morning and becoming fine. Light winds. 23C high, 16C overnight.
Nelson: Periods of rain, clearing by evening. Northerly breezes developing morning. 21C high, 17C overnight.
Christchurch: Occasional rain clearing to fine spells by afternoon. However, some low cloud at night. Northeasterly breezes. 18C high, 14C overnight.
Dunedin: Fine, with high cloud at times. Chance fog in the evening. Northeasterly breezes. 21C high, 16C overnight.