The second low, which is set to arrive at the weekend, could bring torrential downpours, Mr Duncan said.
However, the coldest days of winter are over and the storm is unlikely to be accompanied by low temperatures, he said.
Metservice meteorologist Daniel Corbett said the procession of weather systems will maintain an "unsettled theme" in the weather across New Zealand
Rain will hit northern and eastern New Zealand from Tuesday until Thursday, with some thunderstorms are likely in the northern half of the North Island, he said.
"With several different weather systems to come, it will again be a week where we keep the raincoats close to hand."
The end of the week will be drier, before another active system moves over the country, Mr Corbett said.
- HERALD ONLINE