There have only been five emergency declarations in Northland since 1973.
What should you do?
Emergency management has urged people to stay home, avoid non-essential travel and not drive through floodwaters.
Councils have also asked people not to try to walk or swim in floodwater, as it may contain sewage.
If you come into contact with floodwater, wash your hands and clothes when you can.
What if your home is flooded?
If you need to evacuate your home, emergency management advises staying with friends or family if possible. No information on emergency shelters in Northland is yet available.
Remember to take essential items such as medicines, warm clothing and baby items.
People are advised to take their pets with them as well as water, food and other essentials for them such as leads and carry cages.
Te Kahu o Taonui spokesperson Huhana Lyndon said five marae had been open on Monday night for anyone who needed emergency accommodation, and they would remain open.
Cleaning up after flooding
After the flooding on Friday, Auckland Council advised wearing protective clothing while cleaning up and washing hands thoroughly afterwards.
Residents in affected areas should also throw away any food and drinking water that has come into contact with floodwaters. Garden produce should not be eaten if soil has been flooded.
Keep children and animals away from areas that have been flooded until they are cleaned and made safe.