Bay of Plenty has recorded its wettest day of the month so far, with more heavy rain forecast and warnings in place as a slow-moving weather system brings flooding and slip risks across the region.

MetService says some weather stations have already recorded more than 50mm of rain in the 12 hours to 11am on Thursday, with persistent downpours expected to continue into the weekend as a low-pressure system stalls over the Tasman Sea.

Officials are warning of rising rivers, surface flooding, slips and hazardous driving conditions, while a cold southerly change later in the weekend could bring a sharp drop in temperatures and widespread frosts.

MetService meteorologist Ethan Walton-Jones said a low-pressure system in the Tasman Sea was causing the weather pattern to stall, resulting in persistent rain across northeastern parts of the North Island.

“These rainfall amounts bring the risk of rising rivers and streams, surface flooding, slips and dangerous driving conditions,” Walton-Jones said.

“Avoid low-lying areas and drive to the conditions.”

Heavy rain watches and warnings are in force across parts of Bay of Plenty from Thursday evening, with the wet weather expected to continue into Sunday.

The unsettled conditions are forecast to affect much of the upper North Island, while Gisborne north of Tolaga Bay could receive between 90mm and 120mm of rain.

Low cloud and fog are also expected to develop overnight on Thursday, particularly across Auckland and Waikato, potentially affecting travel on Friday morning.

While the Bay of Plenty grapples with heavy rain, forecasters are also warning of a sharp change in conditions later in the weekend.

A cold southerly system is expected to move north from the South Island on Saturday before spreading over the North Island on Sunday, bringing a noticeable drop in temperatures and the possibility of widespread frosts.

There is also a risk of snow in elevated and inland areas of the South Island, and potentially the higher parts of the North Island as colder air arrives.

MetService is encouraging people to stay up to date with forecasts and weather warnings and to take extra care on the roads as conditions deteriorate.

For the latest forecasts and warnings, visit MetService.com.