Greymouth has been flooded after the West Coast region was hammered by rain following a period of drought.

The town was flooded on Thursday morning after 24 hours of heavy rain.

And it is only going to get worse with WeatherWatch predicting another 100mm of rain for the region.

"Despite news of droughts being made official in more places today the heavy rain is too much of a good thing with flooding occurring," WeatherWatch said.

The rain is still welcome for the Buller and Grey districts, which were added to the list of drought-hit areas earlier this week.

A heavy rainfall warning is in place for the Buller district through to Friday morning, with up to 130mm expected to fall on top of what's already fallen in the area, MetService forecaster Cameron Coutts said.

Meanwhile in Westland, from Franz Josef northwards, there has been plenty of wet weather, with 78mm falling at Hokitika since Wednesday morning.

The rain will be a relief for farmers who have been struggling with the dry weather, but the rain might be too late for some.

"I think (the rain's) come too late for Buller, but it will help with getting things growing - it's been dry for some time - it's certainly going to help," Mr Coutts said.

On the other side of the South Island, Canterbury has been experiencing steady rainfall since Wednesday morning.

Christchurch has seen it's average rainfall of 40mm for the month fall in just two days, with 45mm reported at the airport.