Do you have photos or videos of the storm?
Gisborne Civil Defence is urging "extreme caution" as heavy rain continues across the region.
Although the rain is expected to ease by the early hours of the morning, another 100mm is predicted for the worst-affected areas.
In the past 24 hours, about 200mm of rain has fallen in some areas north of Tolaga Bay and inland of Anaura and Tokomaru Bays, and more than 140mm close to the city.
Gisborne Civil Defence controller Jon Davies said drivers need to take extreme caution on roads throughout the district, particularly on the state highways north of Tolaga Bay and at Te Karaka.
"Extra care will still be required tonight and tomorrow due to continued water seepage and flow from rivers and streams across roadways," he said.
Families have been evacuated this afternoon from Tolaga Bay, near Gisborne, as flood waters continue to rise - forcing a driver to take refuge on his truck roof.
Heavy rain is lashing the North Island's East Coast, leaving dozens of homes without power and closing rural schools and roads.
The Hikuwai River, north of Tolaga Bay, crept close to 12 metres, flooding across State Highway 35 and isolating communities, Gisborne civil defence controller Jon Davies said this afternoon.
At least 30 families in the Mangatuna, Wharekaka, Paroa and Mangaheia areas were evacuated, he said.
"We are keeping a close watch on rivers and surface flooding throughout the district. Some of the worst affected areas are between Ruatoria and Tolaga Bay where there has been more than 200mm of rain in the past 24 hours," he said.
He advised people driving home from the city this evening to take "extreme care".
"We have already had one truck stuck in the middle of a flooded road at Ngatapa requiring the occupants to sit on the roof to wait for help.
"In another instance, a car hit surface flooding at speed south of Tolaga Bay causing it to flip and roll into the paddock, fortunately with no injuries," Mr Davies said.
Surface flooding had closed several roads on the Gisborne Flats. Mr Davies advised people to check the council website for road closures before returning home to rural areas.
"There is extensive flooding across the flats but as far as we know houses are not endangered. We advise people not to drive around in the rain unless essential. If it is necessary to drive, be very aware of surface flooding on the roads."
Mr Davies also advised farmers to take precautions with stock and their own personal safety.
A lot of rural schools were closed across the region and all of the children in the city who usually went home by rural bus were sent home this afternoon.
Power company Eastland Network is working to restore power to homes around Gisborne city.
Several roads were closed at Tolaga Bay and in Ngatapa Valley, and more were expected to shut if the rain continued at the same level, Mr Davies said.
Gisborne District Council staff were checking river levels and details were provided on the council's website.