Niwa's Chris Brandolino said areas around Manawatu and Whanganui were also at critical near-drought levels.
Much of the lower North Island, along with Taranaki, Napier and Hastings, was either dry or very dry.
He also confirmed the country was in a La Nina weather pattern for summer, which was characterised by higher pressure than normal to the south and southeast of the country, and lower pressure than normal to the north.
Although the country experienced La Nina last summer, each was different, bringing with it their own weather patterns.
"La Nina doesn't happen in a vacuum," he said.
MetService confirmed the area is in line for some light, but steady, showers for most of the day tomorrow.
The rainfall is the remnants of the front currently giving the West Coast and Fiordland a good soaking after a couple of weeks of dry weather.
Weatherwatch.co.nz said Fiordland - one of the wettest places on earth - has had less rain that desert parts of central Australia over the past 30 days.
Fiordland averages between 14 and 18 metres of rain a year, while areas around Alice Springs are thriving due to the unusual early summer downpours.
Met Service duty meteorologist Andy Best said there was a juxtaposition of activity in the South Island yesterday, with the West Coast getting a whopping 250mm of rain, while the East Coast remained dry.
Christchurch had been clocking up some high temperatures in recent days, peaking at 33 degrees on Friday, and 31 over the rest of the weekend.
However, duty forecaster Tom Bell said temperatures across the country will also ease slightly later in the week as the southerly makes its way up the country.
As for today, the South Island will continue to get some rain as it moves its way north, but the rain would get lighter.
"We have a front moving up the South Island ... It's mostly going to affect southern areas, Southland, Otago and the West Coast today, looks like that's going to progress further northeast tomorrow, so Canterbury, Christchurch, can see some rain tomorrow."
Bell said it wouldn't be huge, but "it should be a reasonable amount".
Rain is forecast about 8am and will fall lightly throughout the day.
Thunderstorms are likely in the central North Island, around Bay of Plenty, Rotorua and eastern Waikato.
"There's a weak front sitting over Taranaki and Waitomo area at the moment and that's due to slowly move north and bringing some light showers. There may be a few showers also for the rest of the North Island and afternoon from about Manawatu, Whanganui northwards."
Thunderstorms were less likely in Auckland, he said.
The humid weather will also continue, he said, which was the result of warm, moist air coming down from the tropics.
Wellington is set to have another scorcher day with just a few northerlies, and the possibility of showers on Wednesday which would not have any effect on the dry conditions.
TODAY'S TEMPERATURES
Whangarei 25C
Auckland 25C
Hamilton 25C
Tauranga 24C
Wellington 22C
Christchurch 29C
Dunedin 22C
Queenstown 20C
