MetService meteorologist Daniel Corbett said the active sub-tropical low would spread spells of rain and gales across many parts of the country.
"It is going to be wet and windy," he said.
"We could easily see 20-50mm of rain in Tauranga and 50-70mm in the Coromandel.
"Winds will be getting up to gales."
Mr Corbett said the gales could reach speeds between 70km to 80km in the Bay.
The warning stated southwest gales were expected to become severe about exposed parts of Coromandel Peninsula and the Western Bay of Plenty in the Kaimai Range today.
Mr Corbett said there was also a risk of local flooding for the Bay region.
The New Zealand Transport Agency is urging motorists travelling around the Bay of Plenty and Waikato region to take care because of the heavy rain warning.
The Transport Agency said roads could be very slippery after a long dry spell, due to a build-up of dust, dirt and oil.
"Conditions are at the worst in the first few hours of rain, and light rain is more of a challenge than a heavy downpour."
Mr Corbett said the bad weather would most likely clear up from tomorrow.
Dry and clear weather is expected for the end of the week "slowly building a high" where temperatures are estimated to reach up to 24C.
Get the latest forecast for Tauranga here.