Thomas Fire

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. 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. It was surpassed by the Ranch Fire, part of the Mendocino Complex, in August 2018. The fire is currently the eighth-largest wildfire in modern California history, as of 2025. The fire was officially declared out on June 1, 2018, after more than two months in which no hotspots were detected. 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. As of August 2020, the Thomas Fire is California's tenth-most destructive wildfire. Ventura's agriculture industry suffered at least $171 million in losses due to the Thomas Fire.

By January 2, 2018, the Thomas Fire had cost over $204 million to fight, and had forced over 104,607 residents to evacuate. 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.^{[needs update]}

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. Though the fire started near the college, no buildings at the college were burned in the fire. The fire quickly reached the city of Ventura, where over five hundred residences were destroyed that night. The fire destroyed almost as many residences in several rural communities amidst the rugged mountain terrain of Ventura County. The fire threatened the Ojai Valley, and on December 13, the fire completely surrounded the area, including Lake Casitas. 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. 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 unusually strong and persistent Santa Ana winds were the largest factor in the spread of the fire. 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 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. At its height, the wildfire was powerful enough to generate its own weather, qualifying it as a firestorm. There were periods of time when the fire was advancing at a rate of an acre (0.4 ha) per second. The winds also dried out the air, resulting in extremely low humidity. The area, along with most of Southern California, experienced the driest March-through-December period on record.

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. With the natural vegetation burnt, flash floods and mudflows damaged homes in Montecito when the rains arrived. Evacuations were ordered or anticipated for neighborhoods that sit below areas recently burned by the Thomas Fire and other wildfires. By January 10, at least 21 people had been killed by the sudden flooding and debris flows that followed the heavy rains, which also destroyed over 100 homes.

On December 4, 2017, the fire was first reported by a nearby resident at 6:26 p.m. PST, to the north of Santa Paula, near Steckel Park and Thomas Aquinas College, after which the fire is named. That night, the small brush fire exploded in size and raced through the rugged mountain terrain that lies west of Santa Paula, between Ventura and Ojai. Officials blamed strong Santa Ana winds that gusted up to 60 miles per hour (97 km/h) for the sudden expansion. Soon after the fire had started, a second blaze was ignited nearly 30 minutes later, about 4 miles (6.4 km) to the north in Upper Ojai at the top of Koenigstein Road. According to eyewitnesses, this second fire was sparked by an explosion in the power line over the area. The second fire was rapidly expanded by the strong Santa Ana winds, and soon merged into the Thomas Fire later that night. According to statements released by investigators on March 13, 2019, Southern California Edison was responsible for both ignitions.

Late on the night of December 4, the Thomas Fire reached the hillside neighborhoods of Clearpoint, Ondulando, and Skyline in the city of Ventura and destroyed many single-family detached homes. Many people fled with little or no warning when evacuation orders were issued, as the fire had traveled 12 miles (19 km) in just a few hours.

Tuesday morning, on December 5, saw 1,000 firefighters battling the blaze, with no containment of the fire. At 7 a.m. PST, one helicopter began dropping water, while fixed-wing aircraft waited to be deployed after the winds died down. The firefighters tried to save Ventura homes in the midst of a red-flag wind advisory with ridgeline winds of 35 to 45 miles per hour (56 to 72 km/h) and gusts up to 70 miles per hour (110 km/h). The fire continued jumping across the valleys along the steep slopes of the foothills that abut the northern portion of the city. As the fire traveled along the interface between the foothill rangeland and the area developed with homes, it reached the hills above downtown where several apartment buildings and other homes above downtown Ventura were damaged or completely destroyed. The fire burned over Grant Park above City Hall, and burned along the ridge above the western portion of the city, which stretches north along the narrow Ventura River valley, and is characterized by steeply-sloped sides.