The wildfires burned over 307,900 acres (1,246 km2),[4][5][6][7] and caused traffic disruptions, school closures,[8] hazardous air conditions,[9] and power outages;[10] over 230,000 people were forced to evacuate.

Fanned by Santa Ana winds, over the next few hours it rushed 12 miles (19 km) across rural backcountry into the city of Ventura, burning close to 500 homes and consuming 50,000 acres (200 km2).

Over the next days, it advanced toward Ojai and had jumped Highway 33 and the Ventura River into the Rincon Oil Field area.

The Thomas Fire had also destroyed at least 794 structures while damaging 187 others, and cost at least $38.4 million to fight,[28][63] becoming at least the 10th most destructive wildfire in California history.

[76][77] Afterward, Los Pedros National Forest officials continued monitoring the burn area of the Thomas Fire for hotspots.

[79] On December 5, at 12:28 p.m. PST, a wildfire broke out near University Parkway and Varsity Avenue in San Bernardino, just off Interstate 215.

[36][39] The wildfire quickly grew to 100 acres (40 ha), causing the closure of Interstate 215, and triggering evacuation orders for residents in the area.

[38] At 6:30 p.m. PST on the same day, the road closure and the evacuation orders had been lifted, though the Little Mountain area still remained closed off.

Firefighters made progress on the fire that day, due to the weakening of the Santa Ana winds in the area beginning on the evening of December 5.

[82] The small brush fire burned 2 acres (0.81 ha) before it was fully contained on the same day, damaging a daycare center and a bank.

[84] On December 8, at 9:30 a.m. PST, the Sweetwater Fire broke out in eastern San Diego County, south of Interstate 8 and just west of Japatul Valley Road, in Descanso.

[50][86] On December 8, around 2:15 p.m. PST, a small brush fire broke out in Otay Mesa Canyon, in southern San Diego County.

[94][95] On December 19, at 8:20 a.m. PST, a small fire broke out at San Diego International Airport, near the 4000 block of Pacific Highway.

"This is a tragic reminder of the dangerous work that our firefighters do every day," said Los Padres National Forest Supervisor Teresa Benson in a release.

Due to the lack of trees' roots holding the soil together, the ground had reduced stability and was vulnerable to mud slides in heavy rain.

In early January 2018, heavy rain was predicted for the American Southwest, causing flash flood watches and evacuations to be issued for portions of California affected by wildfires.