"It's a blocking high and weather systems can't go through it," Bell said.
The weather system was beginning to run out of energy, he said.
The South Island and southern parts of the North could expect showers, with fine breaks, moving toward the weekend.
Some areas had heavy rain yesterday. Happy Sams on the Anatoki River in Golden Bay near Nelson received 333mm of rain in 24 hours, while Mt Taranaki was doused with 250mm.
Heavy rain warnings were in place in Auckland until 6am today, and Northland and Taranaki until midday.
Today's forecast
• Whangarei: Rain, possibly heavy. NE. High 25C Low 20C
• Auckland: Rain easing to showers. NE. High 25C Low 20C
• Hamilton: Rain easing. NE. High 25C Low 17C
• Tauranga: Cloudy with occasional rain. N. High 24C Low 20C
• Wellington: Showers clearing to sunny spells. N. High 24C Low 18C