Weather: Heavy rain, lower temperatures over the weekend in South

A cold change is coming for the South Island and will bring heavy rain and colder temperatures over the weekend. Photo / Supplied

A cold change is on its way to the South Island, bringing heavy rain and colder temperatures over the weekend.

Forecaster WeatherWatch is predicting a "deluge" of rain will fall mainly on the West Coast over the next few days.

Over 200mm is forecast to fall within three days, a spokesperson said.

"This is quite a bit, but for the West Coast, it should be mainly manageable if spread over those days. However, there is the chance for localised slips, flooding and even road closures."

The rain is also expected to spill over into Canterbury.

"Temperatures also tumble on Saturday as a southerly change moves up the South Island.

"Daytime maximums will be more than eight degrees below normal for parts of Canterbury and several degrees below normal for many other southern and eastern areas."

According to MetService, Christchurch is expected to reach 16C on Saturday, a sharp contrast to the 25C expected to be recorded on Friday.

It is a completely different story in the North Island as it continues to lean several degrees warmer than average for many regions, they said.

"It also leans drier than normal for the next several days ahead."

The blast of cold weather is being driven by a heavy rain event out of Australia and partially fuelled by the subtropics.