Level 3 restrictions prohibit the use of outdoor hoses.
It means all residents and businesses connected to the FNDC's treated water supplies can only use a bucket to water gardens, and wash cars or boats.
Filling private swimming pools from FNDC water supplies is completely banned.
The National Institute of Water and Atmospheric Research (NIWA) is predicting lower than normal river levels and soil moisture in Northland right through to May 2019.
"Despite some recent rainfall, the normally resilient Tirohanga Stream catchment has not recharged. Water consumption in both towns has also remained relatively unchanged from
peak summer levels," FNDC general manager infrastructure and asset management Andy
Finch said.
He said the restrictions would hopefully delay, or avoid altogether, the need for more stringent restrictions in future if conditions remained dry as predicted.
To help conserve precious water supplies, Finch is urging all Far North residents and businesses to adopt simple conservation measures.
They include collecting water from the hot tap while waiting for it to heat up and using this in your garden, only washing clothes when you have a full load.
A washing machine uses up to 150 litres of water for one wash.
Also, Finch said people should turn off the tap while brushing or shaving, putting the plug in the sink when washing vegetables, and mulching their garden with grass clippings or compost.
Mulch prevents up to 70 per cent of water loss through evaporation.
Finch said residents concerned about restriction breaches or water leaks should contact the FNDC on 0800 920 029.
There are currently no water restrictions in Whangārei.
"While the river levels are low, the Whau Valley Dam is at 76 per cent and the Wilsons Dam in Bream Bay is at 81 per cent which should be enough to see us through to winter,"
Whangārei District Council water services manager Andrew Venmore said.