Bridges north and south of Mafeking have been severely damaged, which means none of the 130 residents can leave by road.
Robert Hanson, reeve of the Rural Municipality of Mountain, says the ambulance station has been closed because the ambulance is outside the community and cannot get back.
Hanson says anyone needing medical care will have to be taken out by medical helicopter.
Heavy rain late last week combined with melting snow, which has caused rivers to surge.
Hanson says he and others in Mafeking may be able to leave in three days, when a bridge to the north is expected to reopen.