She also urged them to wear masks, stay distanced and stay away from other groups
This change is a part of the Government's three-part road map for Auckland to transition "safely and carefully" over the coming weeks.
She said outdoor gatherings was the safest option - and pleaded with Aucklanders to keep those meetings with other people outside.
Asked about the easing of restrictions given higher case numbers over the last few days, Ardern said the decisions relied heavily on health advice.
On top of outdoor gatherings, people can move around Auckland for recreation such as beach visits, hunting and outdoors yoga.
The health officials had looked at individual restrictions to see which had the least risk attached to them, and could make people's lives easier.
Ardern said they were comfortable in allowing two households, up to 10 people, to meet outside.
Where to get a vaccination in Auckland - without a booking
A similar rollout has been seen across the ditch in Sydney. Last month it was announced fully vaccinated Sydneysiders were allowed to meet for picnics outside.
Ardern said she was relying on people to follow the rules - and stick to the level 3 rules other than the few eased restrictions.