It is going to be exceptionally hot this weekend in New South Wales, with much of New Zealand benefiting from it on Sunday and/or Monday.

Australia’s weekend heat wave is being forecast to break September records, with temperatures soaring as high as 40 degrees Celsius inland and even Sydney may hit 36C.

Their Government forecaster – the Bureau of Meteorology – says if the 40 degree temperature is reached on Saturday through inland NSW it will be the first time in history the State has reached 40 degrees C in the month of September.  

With such high temperatures a full five months out from the hottest time of the year it’s possible Australia could be seeing summer heat that breaks all sorts of records, possibly even international ones. The bush fire season also looks to be severe.

But back to this weekend. The heat on Saturday in Sydney will drift over the Tasman Sea and head to the South Island on Sunday, then the North Island on Monday.

“In my experience if there’s a heatwave in eastern Australia and their wamrth reaches parts of New Zealand we roughly shave off about 10 degrees from their extremes” says WeatherWatch.co.nz head weather analyst Philip Duncan. “The air loses a lot of warmth as it leaves hot inland Australia and crosses over the cooler waters of the Tasman Sea. It then warms back up again a bit as it crosses over the ranges of New Zealand, eg as a nor’wester”.

Reliable data WeatherWatch.co.nz uses suggests inland Hawke’s Bay may reach the mid 20s on Monday, but the nor’wester will heat up some areas even higher. “If New South Wales is heading to 36 to 40 degrees this weekend it’s fair to suggest that the east of the North Island will climb into the mid to late 20s  says Mr Duncan. “I don’t expect 30 degrees, but, I also can’t rule it out as the ingredients are there under perfect conditions to climb that high”.

Perfect conditions being the warmest of the Australian air reaching New Zealand in the afternoons with clear skies and the right wind flow (north to north west in the South Island and nor’west for the North Island).

The forecast high for Gisborne at this stage is 25 degrees on Monday – but places further inland may get closer to 30. Or possibly 30. Hasting’s current forecast high is 26 degrees.

Meanwhile the South Island gets the warm winds earlier, on Sunday. There may be extra cloud around which reduces the heat though. Southland, Otago, Canterbury and Marlborough are all expected to reach the 20 degree mark with some making the mid 20s if conditions are sunny and windy from the north to north west during the afternoon. “Again we may see some areas go a bit higher if the sun is out and windflow is coming off the hills at the right angle to create additional heat”.

New Zealand’s complicated geography means not all will feel the heat – those along the Tasman Sea coastline won’t be as warm as those in the east will be.

Oh and Sorry Wellington – by the looks of it you miss out on this warm weather, out of the 6 main centres you’re most exposed to the cloud and cooler winds straight off the Tasman Sea/Cook Strait area. It’ll be fairly typical windy spring weather for you.

Next week cools down faster in the South Island on Tuesday but the North Island stays fairly mild.

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3pm Sunday:

3pm Monday:

– Afternoon Temperature maps / Weathermap

– WeatherWatch.co.nz