Residents have also been asked to try to save 30 litres of water a day each - the equivalent of three or four full toilet flushes.
Only 19 days of water are left in the city's reservoirs, and authorities are looking to draw water from the Hutt River as a last resort.
So far, Northland, Waikato, Bay of Plenty and Hawkes Bay have been declared drought-affected.
Wairarapa, Manawatu-Rangitikei, Taranaki and Gisborne have also asked for help.
The Government will give further notice of drought relief when Primary Industries Minister Nathan Guy visits Manawatu this morning.
Wairarapa farmers told Labour leader David Shearer yesterday that production would double if winter water could be captured and stored.
Wairarapa Federated Farmers president Jamie Falloon said although dairy farmers were facing decisions such as relying totally on feeding out and of drying off herds early, sheep farmers had culled their ewes, sold off surplus lambs and were contemplating whether they would have to sell off capital stock.
On the West Coast where drought is "highly unusual", farmers are being urged to take up offers of support.
Federated Farmers said most would have no idea how to cope with the drought or its aftermath and advised sharemilkers and their bosses to jointly plan the 2012/13 season's end to manage its effects. This drought was "significantly different" to the last one, said Federated Farmers sharemilker employers vice-chairman Tony Wilding. "There are very few places where farmers can send stock to which has enough grass, even in the South Island," he said.
Cyclone Sandra is expected to bring rain to most places this weekend - the first decent fall since mid-January - with showers on Monday.
The rainfall is a step in the right direction but much more is needed to pull the country out of the grip of widespread dry conditions.
In North Otago all fire permits will be revoked and a prohibited fire season imposed if it doesn't get any rain from Cyclone Sandra.
Saving tips
Watercare's water-saving suggestions:
* Use a watering can rather than a hose.
* Fix leaks.
* Take shorter showers.
* Use washing machines only when they have a full load.
* Turn off the tap while brushing your teeth.