On August 11, a lightning strike ignited a fire in the Three Sister Wilderness west of the small town of Sisters. Initially, it was allowed to burn because it was in a remote part of the wilderness and firefighting crews were already deployed on other higher priority fires. By August 13, the Milli Fire had grown to . Initially, a seven-person helitack crew rappelled into the fire area and began fire suppression work near Black Crater Lake. Later, an additional 15 firefighters were assigned to the fire along with four bulldozers and two excavators. During August 14-16, the fire grew to approximately . As they fought the blaze, crews had to use extreme caution because the fire was burning across some areas scarred by the 2006 Black Crater Fire which had thick brush and dead standing timber.