It’s the middle of winter and the overnight lows in some of our coldest regions are above zero. It may not be by much, but right now it should be colder.

Under clear skies and light winds, at the end of July, the lower South Island should be in serious frost territory. Instead the forecast this week is unusually mild once again. Take Alexanxdra in Central Otago for example. Monday to Saturday next week has mostly light winds and clear skies, usually the perfect recipe for some heavy frosts. The overnight lows are forecast to be around +2 and +3. Queenstown is similar, +1 to +3.

Further south in Northern Southland and Lumsden has lows of +2 to +4, the same as Wanaka for those same days next week.

Normally by now places like this have had some severe frosts and are getting plenty of good hard frosts. But that is not the case at the moment. Instead of -4 to -7 places are +4 to +7. 

The North Island is even warmer with traditional cold spots like Taupo between +3 and +5 this Monday to next Saturday. Hamilton is +2 to +6. 

Part of the reason for the warmer weather has been the placement of highs and lows, encouraging far more warmer westerlies and sub-tropical northerlies over our small nation over the past few months. But it’s hard to argue the trend that has formed this decade. Each winter since 2011 has become warmer and warmer with no serious temperature trends going the other direction. Clear skies in late July (the coldest point of the year) should produce big frosts through the inland South Island. 

We’ll have to wait until later in September before the verdict is out about Winter 2019 and why we’ve had a lack of frosts. Also, we are only at the halfway point of cold – more frosts are possible in August and September and it’s possible they could be severe. But the window for severe frosts in New Zealand starts to close around mid August. That’s now less than a month away.

– WeatherWatch.co.nz