Last weekend New Zealand continued in the southwest weather pattern that has lingered around since December.

This means that the South Island west coast got most of the rain at the weekend while parched regions in the north and east hardly saw a drop.

Many areas in the east and north will have fine weather for the next couple of days, with 28C forecast for Tauranga and 29C for Christchurch on Tuesday.

However, on Wednesday there is a rapidly deepening low approaching from the west. 'This low is set to undergo a process called ‘explosive cyclogenesis' by meteorologists. This means the low will deepen very rapidly in a short time,” says communications meteorologist Lisa Murray.

'When a low has an intensification (a change in central pressure) which exceeds a certain amount in 24 hours it can be defined as a ‘bomb' low.”

Lisa says this low meets the 'bomb' criteria and is forecast to bring damaging winds to exposed parts of the South Island and lower North Island, and extremely heavy rain to the South Island west coast later Wednesday.

'It's important people realise that although there has been heavy rain in these areas recently, this low brings large accumulations of rain, up to 300mm in 24 hours for some of the ranges, which could cause widespread flooding, slips and damage to roads.”

As the low moves off the country to the east on Thursday it drags up an unseasonably cold southwest flow from the south causing overnight temperatures on Thursday and Friday to plummet back to single digits, with some areas dropping to four degrees.