Rotorua Lakes Council's Emergency Operations Centre has been activated and Civil Defence teams have been mobilised.

The rainfall has also overwhelmed the sewerage system, and the council said all surface water should be treated as contaminated. It's caused overflowing and diluted sewage to overflow the system, entering the stream and lake.

The city's Civil Defence controller Bruce Horne says heavy surface flooding was affecting roads and the sewerage system.

"We haven't got any roads closed yet but we have had some roads that have been affected by the volume of water so we're getting those checked out by contractors at the moment.

"Our stormwater and sewerage has been placed under a lot of pressure. At the moment we're coping, but just.

"There's one or two people that have seen it this bad before but most of us haven't."

Bruce says the rain had started to ease, but it was not over yet.

"There was a lot of surface flooding which rose up very quickly, a lot of that has now subsided which we're very grateful for, but we're mindful we've still got a bit of bad weather to come, we're not out of the woods yet."

Fire and Emergency crews have had more than 100 call outs to flooding-related jobs throughout the day.

Northern shift manager Scott Osmond says off-duty crews had been brought in, and about 30 fire officers were working to help people whose homes had flooded.

"We started at about 8.30 this morning in the Rotorua area and since then we've had about 140 call-outs to various emergencies but almost all is in relation to the rainfall."

"Unfortunately there's been a lot of cases where we haven't been able to do much because the water level's up outside anyhow so there's no point pumping water into more water."

Scott says crews would remain on standby.

"There is another rain band heading towards that area so the weather warnings are in force until late tonight or early in the morning."

There had been widespread surface flooding throughout the city, the council said.

Trees are down, there are slips on several roads and water is flooding properties and entering some homes and garages.

Stormwater covers have popped up in some places and residents have been urged to drive only if absolutely necessary.

Crews from Infracore, Fulton Hogan, Higgins and Fire and Emergency New Zealand have attended more than 60 flooding issues and are prioritising where there is a danger to people and their properties.

Coromandel flooding

Coromandel residents are being asked to take care as heavy rain hits the east of the peninsula.

MetService was expecting another 60 to 90 millimetres to fall, on top of the rain the area's already had.

More than 165mm of rain has fallen in the past 24 hours (as at 10pm) with surface flooding closing some roads between the Peninsula and Waihi.

MetService has forecast 25 to 40mm of rain per hour in Coromandel this afternoon.

Flooding has closed the road between Whiritoa Beach Road and Whangamatā.

Coromandel Thames District mayor Sandra Goudie says there was likely to be a lot of weekend traffic in the area, and people should drive cautiously and be aware of the conditions.

The Transport Agency is advising motorists to take extra care when driving between Whangamatā to Whiritoa along State Highway 25, where there is surface flooding.

Thames-Coromandel Civil Defence controller Garry Towler says more roads could be closed and with high tide around 6.20pm this evening, more surface flooding was likely.

MetService says there was a risk of severe thunderstorms in Coromandel Peninsula and Bay of Plenty on Sunday afternoon, bringing with it surface and or flash flooding, slips, and hazardous driving conditions.

-RNZ