MetService is warning eastern parts of the North Island could experience a potentially "significant rain event" over the next two days.
Metservice issued the warning just before midday on Tuesday saying a band of rain fuelled by warm, subtropical air will bring a risk of significant flooding in Bay of Plenty and Gisborne from Wednesday.
MetService said there is the potential for the warnings to be upgraded to a red - which is reserved for only the most severe and impactful weather events.
"Thunderstorms and associated downpours are forecast in Bay of Plenty and Gisborne tomorrow," MetService said.
"Hourly rainfall rates of 45mm are possible in these regions, potentially causing flash flooding.
"These rates can cause surface flooding as witnessed in Auckland yesterday."
MetService currently has a heavy rain warning in place for Gisborne - from 9am on Tuesday to 11am on Thursday - Bay Of Plenty - from midnight Tuesday to 10pm on Wednesday - and Hawke's Bay from 10am Wednesday to 12pm on Thursday.
There is also a heavy rain watch in place for Taupō - from 3am to 9pm on Wednesday - and Tasman west of Motueka from 7pm on Tuesday to 3pm on Wednesday.
"Eastern areas of the North Island are likely in for a run of wet weather as the weather system responsible parks up east of Aotearoa from Thursday onwards," MetService said.
"Showers continue to develop across Aotearoa New Zealand this morning. Some of these showers may be heavy across northern and central regions, with an isolated thunderstorm."
The new warnings come after Waikato, Auckland and Northland were battered by record rainfall on Monday.
NIWA's climate station in Māngere, Auckland, experienced its wettest hour on record between 9-10am on Monday, with 52mm of rain beating the previous record of 36.4mm.
Auckland experienced 4000 lightning strikes in just one hour on Monday - with 700 in just five minutes.
