Satellite map shows browning of North Island

Dramatic satellite images of the country taken a year apart highlight much of the North Island's desperate need for rain as the drought continues.

Relief was expected this weekend with Cyclone Sandra expected to bring rain to most places - the first decent fall since mid-January.

The heaviest falls were forecast for the West Coast of the South Island.

Images taken over recent weeks show how the country has become increasingly brown as drought conditions have spread.

The image taken on Tuesday shows a swathe of dry land from the tip of Northland to Lake Taupo, the lower west and lower east coast of the North Island.

The top of the South Island is also tinder dry.

Green patches can be seen in Taranaki, south of Taupo, the East Coast and Wellington - despite fears of water shortages in the capital.

Climate scientist Jim Salinger said the difference between the images were unsurprising because last summer was one of the wettest on records, and this summer was one of the driest.

Dr Salinger said the North Island had lost only 145mm of moisture from the soil through evaporation this summer - the seasonal average is 236mm.

"So that's well below average."

Weather patterns showed that droughts, especially for the North Island, could become more frequent, Dr Salinger said.

"The satellite images confirm what we're experiencing," he said.

The North Island had not experienced a drought so severe for 70 years.

He said if current weather patterns continue, New Zealand's climate would be similar to the Mediterranean.

"What it means is that if it just doesn't rain for at least four months of the year, it means you have to bring in your water from elsewhere."