MetService issued a heavy rain warning for Wellington and Horowhenua this morning, and there is a watch in place for heavy rainfall on Mt Taranaki.
The national forecaster said to expect 50mm to 70mm of rain to fall, especially around northern Wellington, the Kapiti Coast and the Hutt Valley. Up to 10mm to 20mm of rain could fall an hour.
Rainfall could cause streams and rivers to rise rapidly, and surface flooding and slips were possible, MetService said.
Rain was also forecast for the rest of the North Island today, including Hamilton where the second one-day international between the Black Caps are India is taking place at Seddon Park. Rain is forecast to start at midday in the city, getting heavier around 4pm.
In Auckland, rain is expected later this morning, possibly heavy in the afternoon, with a chance of squally thunderstorms. The heaviest rain is forecast for 2-3pm this afternoon. Temperatures are expected to reach 21C.
Northland and Coromandel could also get heavy rain and possibly thunderstorms.
Rain is forecast for most of the South Island today, though Otago, Southland and Fiordland could get some fine spells.
Looking ahead, showers are expected to clear in the North Island tomorrow and Northland and Bay of Plenty could get dry, fine weather. Auckland is forecast to be cloudy tomorrow, but clouds will clear in the evening.
In the South Island, fine conditions are expected for most of the island tomorrow with some scattered rain possible late in the day, and showers could develop in the west, mainly in Fiordland.
Cloudy, rainy weather is expected for most of the country on Tuesday and Wednesday, with gale northwesterlies forecast in Wellington and Wairarapa.