Brrrrrr! Sub zero temperatures as region shivers into Friday

The temperature has dropped considerably in Bay of Plenty this week. Photo / File

Frozen windscreens and morning frosts are upon us as Bay of Plenty residents woke to a drop in temperatures this morning.

For many centres the mercury struggled to get much above zero, with eastern parts of the South Island and central North Island plummeting to bone-chilling negative territory.

MetService communications meteorologist Lewis Ferris said the low temperatures suggested most of Bay of Plenty would have experienced a frost this morning.

Desert Rd recorded a decidedly chilly low of -5.3C, Taupō got as low as -2.1C, Rotorua 0.4C, Whakatāne 2C and Tauranga 3.7C.

"4C is a pretty good proxy for a ground frost so it is safe to assume parts of Tauranga would have seen a frost and the rest are more certain," Ferris said.

"Why 4C works is because the temperature reading is taken around 1.4m above the ground and overnight it is the cooling of the ground which cools the air so in most cases the ground will be significantly cooler than the air at sensor height."

On Tuesday, a cold front started its journey up the South Island, passing through Wellington in the early hours of Wednesday and across the North Island through Wednesday," he said.

"Behind the cold front was, funnily enough, a decent burst of cold air brought in by the southerly winds at around 4pm on Wednesday.

"This morning was a lot cooler than Thursday as there was basically no cloud cover and very light winds, these are two key ingredients for frost at this time of year."

Today sees a return to more "average" temperatures for this time of year in the Bay of Plenty, which holds through the weekend and into next week.

Periods of unsettled weather are expected until about the middle of next week when "things look to calm down for a bit".

There is also a heavy rain watch in place for the ranges of Bay of Plenty east of Ōpōtiki on Saturday from 6am to 12pm. A period of heavy rain is expected and rainfall amounts may approach short duration warning criteria.

Bay of Plenty low temperatures:

Today:

Rotorua: 0.4C

Taupō: -2.1C

Desert Rd: -5.3C

Whakatāne: 2.0C

Tauranga: 3.7C

Yesterday:

Rotorua: 6.3C

Taupō: 6.1C

Desert Rd: 0.6C

Whakatāne: 9C

Tauranga: 9.5C

Meanwhile, trains in Wellington have been disrupted, with icy overhead conditions causing delays for commuters traveling into the capital from Masterton and Upper Hutt.

Just before 6am, Dunedin airport recorded -5.2C, while Alexandra was sitting at -3.4C and Ashburton was on -2.3C.

MetService is warning of another unsettled spell of weather for the weekend, with a succession of fronts sweeping across the country.

Early next week central and southern New Zealand can expect to be hit by heavy rain, gales, and snow.