Rain is causing surface flooding in parts of the upper North Island, including Auckland.

The Fire Service had responded to about a dozen calls about flooding from Mairangi Bay to Manurewa since midday on Sunday "but it's all pretty minor", Fire Service northern communications shift manager Jaron Phillips said.

"We're talking basements and garages flooded."

At Massey University's Albany campus crews were digging drains to divert water from entering an accommodation block.

Firefighters were also called out to Whitianga to help a woman who could not leave her house due to flooding.

The situation did not appear to be as serious as the woman thought but there was some concern about the garage, Mr Phillips said.

In a severe weather warning, the Metservice says a trough is moving slowly southwards over the upper North Island preceded by easterly winds and a band of rain.

The heavy rain is expected to cause streams and rivers to rise rapidly and may cause slips and surface flooding.

Heavy rain about Coromandel Peninsula and the western Bay of Plenty is expected to spread southwards to the Gisborne region on Sunday night.

Rain should ease in the Coromandel Peninsula and Bay of Plenty north-west of Tauranga at about dawn on Monday.

It will likely continue into Tuesday morning about Gisborne.

For Coromandel Peninsula and the western Bay of Plenty another 100mm of rain may accumulate on top of what has already fallen, while 140mm may accumulate about the hills and ranges of Gisborne, particularly north of Tologa Bay.