According to MetService some of the thunderstorms could bring localised downpours of 25-40 mm/hr.
Rainfall of this intensity could cause surface or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys.
The Northland Regional Council website showed surface flooding had extended to SH10 from the Kaeo River.
MetService meteorologist Ravi Kandula said since 10am there had been just shy of 90mm of rainfall in Kerikeri, 80mm in Kaikohe and 60mm in Kaitaia.
"There is going to be some fairly decent rain through the Eastern Coromandel Peninsula, parts of Auckland will see that overnight.
"The main focus will be north of Orewa and through the Hauraki Gulf there ..."
Strong winds had been confined to areas north of Great Barrier Island but would pick up in Auckland overnight, he said.