The morning will include mostly scattered showers and cloud across the country, except for the most western areas where heavy rain is forecast.
By this afternoon rain will have spread over much of the country, with the heaviest falls in the west of both the North and South Islands.
A severe rain watch is in place for Westland south of Hokitika to 11pm tonight, with up to 120mm forecast in the ranges.
Northwest of Nelson and Mt Taranaki could also see some heavy falls through to this afternoon.
On Saturday and Sunday, a low over the western Tasman Sea is expected to maintain a moist north to northeast flow over the country.
There will likely be heavy rain across the upper North Island Saturday, and in western areas on Sunday, especially in the Bay of Plenty and Gisborne ranges, where it may continue into Monday.
Northwest Nelson and Westland may also see heavy rain Sunday.
"Overall we are in for a pretty unsettled weekend," Ford said.
Temperatures are forecast to stay fairly mild in the North Island due to the northerly flow, with Auckland forecast to hover around 20C through to mid next week.
The South Island however is in for a cool southerly change on Saturday, with Christchurch dropping to a maximum of 14C, and just 11C on Sunday.
Temperatures are forecast to remain in the low teens across the South Island through next week.
On Monday the rain looks to clear over the North Island but there could still be a showery northwest flow.
Today's weather
• Whangarei
Cloudy. Showers developing morning then rain by evening. Northerlies. 22C high, 17C overnight.
• Auckland
Cloudy. Showers developing morning, turning to rain afternoon. Northerlies. 20C high, 16C overnight.
• Hamilton
Cloudy, showers developing in the morning, then rain from afternoon. Northerlies. 19C high, 15C overnight.
• Tauranga
Morning showers then rain from afternoon. Northerlies. 20C high, 16C overnight.
• New Plymouth
Periods of rain, easing to showers evening. Strong northerlies, easing evening. 19C high, 12C overnight.
• Napier
Cloudy, with occasional light rain until evening. Northerlies. 19C high, 13C overnight.
• Wellington
Occasional rain. Northerlies, becoming strong in the afternoon. 17C high, 12C overnight.
• Nelson
Rain developing morning with brisk northerlies, clearing evening. 18C high, 11C overnight.
• Christchurch
Overcast until afternoon with rain at times, then becoming fine and northeasterlies easing. 16C high, 9C overnight.
• Dunedin
Overcast, and rain at times from late morning. Northeasterlies changing to brisk southwesterlies evening. 14C high, 8C overnight.
