Waterton Lakes National Park’s trails and waterways have been closed but the Waterton townsite, home to the historic Prince of Wales Hotel, remains open.
The fire was reported Thursday night in the northeastern part of Glacier National Park and had burned an estimated 2 square miles (5 square kilometers) by Friday.
Parks Canada and Glacier park staff cleared hikers from the area and evacuated the remote Waterton River Campground in Glacier.
The department says staff are monitoring as it approaches Upper Waterton Lake. Flame lengths of up to 100 feet (30 meters) were reported.
Officials with both parks were working to protect buildings.