Update: Frontier Fire in Siskiyou County containment now reaches 100%

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Updated: 6:04 p.m. May 19

First discovered: 26 hours ago, 3:59 p.m. May 18

Initial location: Harry Cash Rd -Cross of Frontier Dr. Montague, Siskiyou County, Calif.

Fire unit: Cal Fire Siskiyou Unit

Fire type: Wildfire

Fire name: Frontier Fire

Frontier Fire initially started 3:59 p.m. May 18 at Harry Cash Rd -Cross of Frontier Dr. Montague in Siskiyou County, California.

Since its discovery 26 hours ago, it has burned 23 acres. As of Tuesday evening, the fire crew has achieved full containment of the blaze. The fire's cause remains under investigation.

Fire containment

What does 100% containment mean?

Note that full containment doesn't mean the fire is completely out. In this case, it means that the whole perimeter of the wildfire has been surrounded by a control line and it is now stopped from spreading. A fully contained wildfire may continue to burn within the containment perimeter but is not likely to spread.

However, there's a significant difference between containing and controlling a wildfire. After the fire is fully contained, the next step is to control it. Controlling a fire means ensuring that the fire can't spread or cross the containment line.

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 May 19, 2026 at 6:30 AM.