Evacuations were ordered or anticipated for neighborhoods that sit below areas recently burned by the Thomas Fire and other wildfires. With the natural vegetation burnt, flash floods and mudflows damaged homes in Montecito when the rains arrived.

While November is the typical beginning of the rainy season in California, the first measurable rain for the area fell on January 8, 2018, more than a month into the fire. The area, along with most of Southern California, experienced the driest March-through-December period on record. The winds also dried out the air, resulting in extremely low humidity. There were periods of time when the fire was advancing at a rate of an acre (0.4 ha) per second. At its height, the wildfire was powerful enough to generate its own weather, qualifying it as a firestorm. The region experienced an on-and-off Santa Ana wind event for a little over two weeks, which contributed to the Thomas Fire's persistent growths in size. Much of Southern California experienced 'the strongest and longest duration Santa Ana wind event we have seen so far this season', according to the National Weather Service. The unusually strong and persistent Santa Ana winds were the largest factor in the spread of the fire.

Firefighters concentrated on protecting the communities of Carpinteria and Montecito in the southern portion of the county as the fire burned in the foothills of the Santa Ynez Mountains where access was difficult. The fire began burning through the rugged Santa Ynez Mountains as it threatened several small communities along the Rincon Coast north of Ventura, expanded into the Los Padres National Forest, and reached Santa Barbara County. The fire threatened the Ojai Valley, and on December 13, the fire completely surrounded the area, including Lake Casitas. The fire destroyed almost as many residences in several rural communities amidst the rugged mountain terrain of Ventura County. Fast-moving, it quickly reached the city of Ventura, where over five hundred residences were destroyed that night. The fire began on December 4, north of Santa Paula, near Steckel Park and south of Thomas Aquinas College from which the fire was named. At its height, the Thomas Fire saw over 8,500 firefighters mobilized to fight it, which is the largest mobilization of firefighters for combating any wildfire in California history. īy January 2, 2018, the Thomas Fire had cost over $204 million to fight, and had forced over 104,607 residents to evacuate. Ventura's agriculture industry suffered at least $171 million in losses due to the Thomas Fire. As of August 2020, the Thomas Fire is California's tenth-most destructive wildfire. The Thomas Fire destroyed at least 1,063 structures, while damaging 280 others and the fire caused over $2.2 billion (2018 USD) in damages, including $230 million in suppression costs, becoming the seventh-most destructive wildfire in state history at the time. The fire was officially declared out on June 1, 2018, after more than two months in which no hotspots were detected. The fire is currently the seventh-largest wildfire in modern California history, as of 2021. It was surpassed by the Ranch Fire, part of the Mendocino Complex, in August 2018. It burned approximately 281,893 acres (440 sq mi 114,078 ha) before being fully contained on January 12, 2018, making it the largest wildfire in modern California history at the time. The Thomas Fire was a massive wildfire that affected Ventura and Santa Barbara Counties, and one of multiple wildfires that ignited in southern California in December 2017. Map of the Thomas Fire and adjacent fires Progression of the Thomas Fire, by December 25, 2017

California fires map december 2017