The southerlies that have plagued parts of New Zealand so far this June will be blown out to sea by an incoming northerly change on Monday and Tuesday as a slow and large low pressure system starts to move in from the Tasman Sea.

WeatherWatch.co.nz says overnight lows will jump up by 10 to 15 degrees for some regions as double digit temperatures replace overnight lows below zero lately.

This morning a significant frost went as far north as the “winterless north”, Northland.  WeatherWatch.co.nz reader “Steve” said it was -2 at his Northland farm this morning.  “First true frost at minus two degrees this morning in lower Northland. Not quite a water trough freeze over but not far off”.

Heavy frosts were recorded across the country today, including Auckland.

But the frosty conditions are coming to a temporary end with WeatherWatch.co.nz head weather analyst Philip Duncan saying warmer weather is on the way along with heavy rain, isolated thunderstorms and possibly localised damaging winds.  “We’re going from weather that was more like the total depths of winter, to something that’s more autumn or spring-like. The change will be noticeable”.

“Warmer northerly winds will spread across the country overnight tonight and into Monday then winds from the northerly quarter should affect most regions for a time then we’ll see more westerlies for the remainder of the week”.

The new detailed forecasts for Christchurch paint a different picture this week than last with a slight shift in wind direction creating a significant change in the forecast.   Highs will be back in the double digits with overnight lows above freezing.  Snow, sleet and hail are not in the forecast for this week.

In Auckland the forecast is a wetter but warmer one with overnight lows jumping by 10 degrees tomorrow night and highs shifting from the low teens to the mid teens – a small change on paper but without any significant wind chill it will feel several degrees warmer at times.

However the mixture of warm and cold air could spark thunderstorms, squalls and even waterspouts or tornados on Tuesday and/or Wednesday says Philip Duncan.

“A very typical mix of warm, moist, air then cooler, drier, air is a great recipe for unstable weather that can produce localised heavy downpours, thunderstorms and even squalls or small tornados in more coastal areas”.

WeatherWatch.co.nz says predicting specific details for thunderstorms more than 12 to 24 hours in advance can be tricky – we’ll be updating each day on this developing forecast – but that northern and western sides of the North Island and northwestern regions of the South Island would be most exposed.

The main rain band may tap into sub-tropical air too, which could prompt some rain warnings in the north and west of the country.

– WeatherWatch.co.nz