"The warning criteria for heavy rain is 50mm in 6 hours, or 100mm in 24 hours.
"There is also low confidence (20 per cent chance) of northeast gales will be severe over southern Westland and northern Fiordland."
Over the North Island, there was moderate confidence, a 40 per cent chance, of significant heavy rain from Taranaki to Tongariro National Park, and low confidence for the Tararua Range.
Over the weekend a new low hanging around the western Tasman Sea was expected to bring rain over parts west of the South Island from Fiordland to Nelson.
"There would be some areas still getting hit by rain until Tuesday.
"There will be bands of rain moving across the country.
"Everyone will get some rain," Haddon said.
Over the North Island there was moderate confidence of significant heavy rain continuing through Saturday and Sunday over the Taranaki to Tongariro area, with low confidence from Northland to Taupo, as the second front moved eastwards.
The Bay of Plenty and the Gisborne ranges had low confidence of significant heavy rain on Saturday, increasing to moderate on Sunday and Monday.