Update: Containment efforts for Thorn Fire in San Diego County hit 80%

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Updated: 6:26 a.m. July 18

First discovered: 3 days ago, 8:45 a.m. July 15

Initial location: Buckthorn Trail and Clover Trail, San Diego County, Calif.

Fire unit: Cal Fire San Diego Unit

Fire type: Wildfire

Fire name: Thorn Fire

Thorn Fire initially started 8:45 a.m. July 15 at Buckthorn Trail and Clover Trail in San Diego County, California.

As of Saturday morning, 1,234 acres of land had been destroyed by it. By Saturday morning, the fire crew succeeded in containing 80% of the fire. There is currently no information on the cause of the fire.

Fire containment

What does it mean for a fire to be 80% contained?

Containment indicates what percentage of the fire perimeter has been surrounded by a control line. In this case, it means that 80% of the wildfire is contained from spreading, while 20% is still uncontrolled.

Containment is part of a larger plan for managing a wildfire. It is normally expressed as a percentage and it refers to how much of the fire perimeter has been surrounded/enclosed by a control line that firefighters create. The containment percentage indicates a certain level of control, but it doesn't always correlate to safety level. Also, it's important to note that containment doesn't mean a fire is out.

How is containment measured?

The incident's central command constantly receives progress reports from firefighters on the ground. As the fireline is constructed, inspected or reinforced, mappers record those details to adjust the containment percentage. The percentage tells the public how much of the fire perimeter is believed to not go beyond the control lines.

Source: Cal Fire

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This story was originally published July 18, 2026 at 6:48 AM.