Weather: What to expect this weekend

It'll pay to do the outdoor chores today if you live in the upper half of the North Island as rain starts to fall at the top of the country.

MetService meteorologist Peter Little said most of the country was looking good today with fine weather forecast over much of New Zealand.

However, rain was starting to fall in parts of Northland and would gradually spread south later today, reaching Auckland late tonight.

The showers were likely to be heavy and forecasters were closely monitoring the situation.

"Today for somewhere like Auckland there will be increasing high cloud after a lovely sunrise but much of the rest of the country is looking good," said Mr Little.

Tomorrow was looking bleak for those in the north and east of the North Island across to the Bay of Plenty with rain falling throughout the day.

The weather was also turning wet at the south of the country with rain coming into Fiordland and south Westland later today before spreading up the island tomorrow.

Mr Little said a ridge remained parked over central New Zealand bringing fine weather to Taranaki and Hawke's Bay south both days.

MetService has issued a severe weather watch for Northland, Great Barrier Island and Coromandel Peninsula with a possibility of heavy rain and thunderstorms over the next 18 hours.

The watch was in place for Northland from this afternoon to early Sunday and elsewhere from tonight through Sunday.

In Northland the heaviest rain was expected to fall in the far north and the eastern hills where localised downpours and thunderstorms were possible.

Coromandel Peninsula could expect to be hit by the subtropical downpours and possible thunderstorms tomorrow afternoon.

Forecasters said heavy, localised downpours could see between 60-85mm of rail fall within 12 - 18 hours.

Meanwhile a wet weather warning has been issued for Fiordland and the ranges of south Westland.

WeatherWatch is expecting most of the rain to be offshore but said it would brush many populated areas.

"The air flow is being pulled down towards New Zealand from south of Tonga and will help spark some very heavy downpours to the north east of the North Island - with the easterly flow pulling this into parts of Northland, Auckland, Coromandel Peninsula, Bay of Plenty, East Cape, Gisborne and to some degree Waikato and Hawkes Bay.

"The low itself is not very aggressive but tapping into the sub-tropical air means downpours heavy enough to cause localised flooding is possible."

Main centres outlook

• Whangarei: Today: Cloudy with rain developing this afternoon. High 22C. Sunday: Rain, some may be heavy. Rain eases in the evening and easterly dies out. High 22C.

• Auckland: Today: Mostly cloudy with a chance shower in the evening and easterly winds. High 21C. Sunday: Rain develops in the morning, with heavy showers possible. Southwest change. High 20C.

• Hamilton: Today: Cloudy periods. Easterlies. High 21C. Sunday: Occasional rain from the morning and light winds. High 20C.

• Tauranga: Today: Cloud increasing. Showers possible in the evening. High 20C. Sunday: Occasional showers from the morning. Northeast winds strengthen. High 21C.

• Wellington: Today: Cloudy periods and fresh northerlies. High 19C. Sunday: Cloudy periods with fresh northerlies easing in the evening. High 19C.

• Christchurch: Today: Fine with northerlies. High 22C. Sunday: Mainly fine but rain with southerly change in the evening. High 20C.

• Dunedin: Today: Fine with high cloud and notherlies. High 20C. Sunday: Occasional rain, clearing by evening. Early southerly change. High 16C.

Source: MetService