Spring breakup has started in the far north, and an ice jam on the Moose River is threatening to flood both Moose Factory and Moosonee.
Moose Factory Island Fire and Rescue officials said the community's hospital is on alert in case patients need to be moved.
Officials in Moosonee also said they are preparing in the event evacuation of vulnerable citizens is necessary.
Emergency Management Ontario reported the town has requested provincial assistance.
People in both communities have been asked to watch for flood updates and prepare to leave quickly, if necessary.
Some evacuations have already been necessary on the James Bay Coast — but they are related to sewer backups.
About 200 people from Kashechewan were flown to Kapuskasing earlier this week because the sewer backed up into 40 homes. Those units have no furnaces or electricity.
At least a dozen homes were also damaged by sewer backup in Attawapiskat, but only hospital patients were removed from that community.