UPDATE: A heavy rain watch has now been upgraded to a warning for the western Bay of Plenty.

Bay of Plenty Civil Defence released a notification saying it had upgraded its status after the MetService upgraded the watch to a warning at 9.34am.

Heavy rain is expected to hit the Bay of Plenty, Coromandel, and Rotorua this afternoon as a low moving east over the Tasman Sea approaches.

MetService reports the heaviest falls are expected about western Bay of Plenty where 70 to 90mm may accumulate about the ranges this evening and early Wednesday morning.

People are advised that heavy rain can cause rivers to rise rapidly, with surface flooding possible in low lying areas.

Bay of Plenty Police are also urging motorists to take care on the roads.

Earlier:

Heavy rain is expected to hit the Western Bay of Plenty later today as a low approaches over the east of the Tasman Sea.

The MetService has issued a severe weather warning for Tauranga and the wider Bay of Plenty.

This watch is for the possibility that rainfall accumulations could approach short duration warning amounts of 70mm or greater in 12 hours.

Downpours are expected in localised areas, about Northland during Tuesday afternoon and evening, and about Auckland, Coromandel Peninsula and western Bay of Plenty from late today into Wednesday morning.

Rain is a result of a low moving east over the Tasman Sea that is expected to spread a band of rain southward over the North Island.

Isolated thunderstorms are possible.

People in the affected areas are advised to stay up to date with the latest forecasts in the event any part of this watch is upgraded to a warning.

This watch will be reviewed by 10am today, reports the MetService.