The heavy rain warning for the Western Bay of Plenty and Tauranga city has now been upscaled to a red alert, a step more serious than the previous orange alert that was issued on January 30.

MetService issued the warning at 2.40 pm on January 31 and advised that a further assessment would be made at 9pm.

A red alert means that the forecast for the region is extremely heavy rain.

'Rain is expected to cause dangerous river conditions and significant flooding. Slips and floodwaters are likely to disrupt travel, making some roads impassable and possibly isolating communities,” said the warning.

The red alert will be in place for 18 hours from 3am Wed 1 Feb to 9pm Wed 1 Feb. MetService is forecasting 100 to 150 mm of rain, especially inland, with peak rates of 15 to 25 mm/h.

Red heavy rain warnings are now in place for Northland, Auckland north of Orewa, Coromandel Peninsula, and now also Bay of Plenty west of Kawerau which includes the Rotorua Lakes District, Western Bay of Plenty District and Tauranga City.

Orange heavy rain warnings are in place for Auckland from Orewa southwards, Great Barrier Island, Bay of Plenty east of Kawerau, and northern Gisborne.

An orange alert level means that 'heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.”

Heavy rain watches are now in place for Waikato, Mount Taranaki, northwest Tasman and Westland.

A watch for severe northeast gales is also in place for Northland and Auckland, with large waves affecting eastern coastlines.

- Annemarie Quill/Stuff.