T-shirts will replace puffer jackets as much of the country basks in "Australian-like" mid-winter temperatures over the weekend.

The brief warm spell comes after a windy and wet start to the week in which trees were torn up, a home was struck by a tornado and a boat ran aground on rocks.

WeatherWatch is predicting a large high off the North Island's east coast would scoop up subtropical air, pushing it down over northern areas on Friday.

Head analyst Philip Duncan said although the end of July was typically the coldest time of the year, it would be unseasonably warm for most of the North Island and some areas of the east of the South Island on Friday and Saturday.

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As the weekend arrives, warm air would arrive from our cousins across the ditch - and it would come directly from the deserts of Australia's interior.

Duncan said the warm air wouldn't be cooled by the Southern Ocean, as it had during a previous high, but would take a "direct flight" across the Tasman Sea, from Australia's east coast to New Zealand.

That would bring "Australian-like temperatures" across parts of the country on Saturday.

The warmest centres would mostly be in the North Island, but also in the east of the South Island, Duncan said.

While all-time monthly records were unlikely to be broken, daily records might be broken on Saturday when maximums are forecast to be anywhere from 5C to 7C warmer than average, reported the National Institute of Water and Atmosphere (NIWA).

Several places may also have their mildest July 23 overnight on record, particularly across the North Island.

Tropical winds from north of Vanuatu would stream southward, allowing temperatures across New Zealand to rise to levels more typically experienced during late spring than mid-winter.

As air blows off the Southern Alps and ranges of the central North Island into the lower terrain to the east, it would warm considerably.

This was known as a foehn wind.

It wasn't all good news, however, as the MetService is still predicting gale force winds and rain this weekend.

With just a day of respite from the blustery winds, those heading back from school holidays on Friday will be hit by strong northerly winds which are predicted to ramp up Saturday to severe gales over much of New Zealand.

The rain is also expected to sweep up the country during Saturday and Sunday, the heaviest falls reserved for northern and western areas.

On Saturday night, total rainfall might range from 75 to 150 mm across the west of the South Island and 50 to 100 mm across the west of the North Island.

Wind gusts in excess of 150 km/h were possible in the west of the South Island, across the Cook Strait and Wellington, and for much of the western and central North Island later Saturday through early Sunday.

Winds of this magnitude may cause power outages, hazardous driving conditions, and minor structural damage.

A burst of strong winds with gusts of 80km/h to 120 km/h was forecast to come across the Auckland region very early Sunday morning.

Total rainfall might range from 75 to 150 mm across the west of the South Island and 50 to 100 mm across the west of the North Island.

From late Sunday, the rain and wind would slowly ease or clear as a narrow ridge moved on to the country.

The bad weather has already kept emergency services busy, as winds of up to 128km/h barrelled through Waikato and Auckland overnight on Tuesday.

Fire Service spokesman Daniel Nicholson said there were more than two dozen callouts as trees were uprooted, blocking roads and bringing down power lines.

The worst damage came when properties were struck by a tornado that tore through Te Awamutu about 8.30pm.

Through to the end of July, mild periods, especially for the east of the South Island and the North Island, would alternate with cool ones.

There were some indications that a more impressive cool snap could come around the start of August.

WARM WINTER FOLLOWS HEAT STREAK

According to the US National Oceanic and Atmospheric Administration, last month's weather marked 14 consecutive months of record heat for the globe.

Worldwide, June 2016 was 0.9C above the 20th century average, breaking last year's record for the warmest June on record.

For the year to date, the average global temperature was 1C above the 20th century average - the highest temperature for this period, surpassing the previous record set in 2015.

NOAA also reported the globally averaged sea surface temperature was record high for June and the year-to-date.

Much warmer-than-average conditions engulfed most of Africa resulting in the second warmest June since 1910 for the continent, while the average Arctic sea ice extent for June was 11.4 per cent below the 1981-2010 average.

This was the smallest June extent since records began in 1979.

The average Antarctic sea ice extent for June was 103,599 sq km below the 198-2010 average, marking the smallest June Antarctic sea ice extent since 2011 and the 13th smallest on record.

Climate agencies expect warming trends to continue in line with climate change, which is projected to increase the globe's average temperature by several degrees by the end of the century.

WARM WEEKEND: DAYTIME AND OVERNIGHT HIGHS ON SATURDAY

• Whangarei 20/14

• Auckland 19/14

• Tauranga 17/13

• Gisborne 19/14

• Napier 19/13

• Taupo 15/10

• New Plymouth 17/11

• Wellington 16/12

• Christchurch 17/8