Rainfall forecasts were being revised upwards last night, and as much as to 250mm was expected to fall in the Eastern Bay of Plenty and Gisborne ranges between 9pm yesterday and 6 o'clock this evening.
Up to 140mm was expected elsewhere, with localised downpours expected to bring 25mm to 40mm of rain in an hour in some spots.
Although the heaviest rain was expected overnight heavy downpours were still tipped for many parts of the country today, followed by possible gale-force winds. The MetService yesterday issued a severe weather warning for the middle of the North Island from Taranaki to the Bay of Plenty, and a severe weather watch for the entire island.
Bay of Plenty emergency management director Clinton Naude said people need to be prepared and make a plan.
"Think about what you and your family would you do if you couldn't get home, were stuck at home or had to leave home in a hurry? Would you be ready?
"What if there was no power, no water or no communication? If there is heavy rain coming, have you cleared your gutters or thought about your pets?
"A little bit of planning goes a long way," he said.
Donna is the third ex-tropical cyclone to hit New Zealand in two months, after Cyclone Debbie devastated parts of the Bay of Plenty last month.
Nervous Edgecumbe residents were being reassured last night that the Rangitaiki River's stopbanks would hold, after they broke and devastated the town on April 6.
Bay of Plenty hazards team leader Rick Liefting said catchments were still saturated in many places after April's cyclones.
"However, council staff are confident that flood management schemes will handle the forecast rainfall."
Liefting said it should start to fine up this afternoon but urged people to stay up to date with weather forecasts and warnings.
WeatherWatch said after ex-cyclone Donna passes by a large high would come from the Tasman, bringing settled weather for three to four days.
The coming weeks may see a similar pattern of lows followed by highs, WeatherWatch said.
Forecast
Whangarei: Heavy downpours today, easing to showers. Strong winds today and tomorrow. H 21C, L 9C.
Auckland: Heavy downpours this morning, strong southerly winds through to tomorrow. H 19C, L 7C.
Hamilton: Heavy falls ease today. Becoming fine tomorrow. H 19C, L 2C.
Tauranga: Heavy downpours ease by this evening. Some heavy rain tomorrow. H 20C, L 7C.
Napier: Heavy falls and possible gales today and tomorrow. H 18C, L 7C
Wellington: Early Friday rain easing to showers through tomorrow. Southerlies, gales on both days. H 14C, L 7C.
