 Around this time, officials and experts feared that the Thomas Fire could surpass the Santiago Canyon Fire of 1889, which had burned over , and is believed to be California's all-time largest wildfire on record.On December 17, the Thomas Fire expanded to , with 45% containment, reaching the burn scar of the 2008 Tea Fire and the 2009 Jesusita Fire.However, the weakening of Santa Ana winds in the evening allowed firefighters to make progress on containing the fire, with firefighters able to keep the Thomas Fire from burning southward into the majority of nearby homes, and they also attacked the western front of the fire.