Temperatures are about to plummet nationwide with snow flurries in both islands, warns WeatherWatch.co.nz.

"While accumulation may not be great for many populated places the chance for snow is there in places like Dunedin and Christchurch, and possible the hilltop suburbs of Wellington," says a spokesperson for the weather organisation

"Cold air may be the main problem with this event though - both for newborn livestock and for those with Kiwifruit orchards and vines. High pressure rolls in by Friday bringing a great weekend of settled weather.

"Australia - We have a special video update for Australia out today, due to a big rain event there.":

Watch WeatherWatch's latest video above.

Here are some of the interesting talking points:

-Lower South Island: Windchill below freezing for 36 hours in parts of Southland - from midnight tonight to noon Thursday. It will feel like -1 to -5 for this entire period.

-Lower North Island: Windchill around freezing, or below it, for 36 hours in Wairarapa - from midnight tonight to noon Thursday.

-Dunedin has a Daytime Max Temperature of just +5C on Wednesday

-Dunedin will have a Feels Like/Windchill of -6 overnight Wednesday/Thursday morning

-Gore has a Daytime Max Temperature of just +3C on Wednesday!

-Queenstown's Daytime Max Temperature is +4C on Wednesday and the overnight low on Wednesday night is -3C

-Arthur's Pass is forecast to drop to a bitterly cold -9C on Wednesday night/Thursday morning

-Tekapo has a high of only +2C on Wednesday and drops to -7C tomorrow night, record-challenging cold.

-Christchurch has some chance of snow - but totals vary from just a trace or rain/snow mix, to up to 5cm, main risk Wednesday night and Thursday AM.

-Wellington has a high of +7C on Thursday but a feels like/windchill temperature of +2C at lunchtime with a southerly gusting to gale force. Dust the winter scarf off.

-Wellington's hill top suburbs have a chance of snow overnight Wednesday/Thursday morning

WeatherWatch.co.nz can't rule out the chance of some sea level snow flakes in the lower North Island in the early hours of Thursday morning - but won't be much, if at all.

The northern most main centres with snow potential (or a rain snow mix) are: Stratford, -Dannevirke, Waiouru and Ohakune. Please note: this doesn't mean heavy snow for all these main centres, but the chance of snow flakes in the main centre (or at least very nearby).

-The northern most areas likely to receive snow are: The Kaimai and Coromandel Ranges - only a small amount (1 to 3cm maybe on the peaks)

-Most likely candidates for sea level snow: Southland, Otago, Canterbury.

-Sleet may fall in Wellington, Napier and Hastings, possibly Palmerston North.

-A huge high pressure system (mostly responsible for this cold blast) will cross NZ over Fri-Sat-Sun bringing settled weather, light winds, cold nights but milder days. Dunedin's high on Sunday is back into the mid-teens.

The 7 day "Departure from Normal" rainfall forecast shows a big portion of NZ leans drier than average in almost every region (other than the West Coast, Southland, Wellington and Wairarapa - all of which have normal rainfall for this time of year over the next several days).