The Lone Star Fire burning in Yellowstone National Park has grown from 3,348 acres to 3,914, according to a release from the park service.
The growth is attributed to spot fires that are creeping and smoldering, with potential for more growth as temperatures remain high and humidity stays low.
The park says a smoky haze will likely be visible in the area as smoke from the local fire mixes with smoke from fires on the west coast.
Article continues below...
The grand loop road between Old Faithful and West Thumb is open but may be closed without warning due to visibility concerns, said the park in the release.
Demand for firefighting resources remains very high, with a Preparedness Level of 5 out of 5.