What starts wildfires? Human activity and lightning in numbers

What starts the most fires?

NIFC recorded 77,850 wildfires in 2025: 69,556 attributed to human activity and 8,294 to lightning. That gives human activity an 89.3% share of reported fires, compared with 10.7% for lightning. These are US figures for a single year, not a worldwide average or a forecast for any particular site.

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People caused most reported wildfires

United States, 2025 · 77,850 reported fires

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United States, 2025. Percentages use the published national total; the CSV retains unrounded values.

Cause	Reported fires	Share
Human activity	69,556	89.3%
Lightning	8,294	10.7%

“Human-caused” covers a wide range of activities. NIFC’s cause categories include campfires, debris burning, equipment and vehicle use, power infrastructure, fireworks and arson. Some ignitions are accidental; others are deliberate. The headline percentage does not tell us how much each activity contributed, so it cannot be read as a measure of arson. Read NIFC’s guide to wildfire causes.

Which fires burn more land?

The burned-area figures show why lightning still deserves close attention. Human-caused fires burned 2,274,333 acres, or 44.3% of the national total. Lightning-caused fires burned 2,857,141 acres, or 55.7%. Together, they account for the 5,131,474 acres NIFC reported burned in 2025.

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Lightning-caused fires burned more land

United States, 2025 · 5,131,474 reported acres burned

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United States, 2025. Percentages use the published national total; the CSV retains unrounded values.

Cause	Reported acres burned	Share
Human activity	2,274,333	44.3%
Lightning	2,857,141	55.7%

How do regions compare?

Location changes the picture substantially. The table below compares the share of reported fires in four NIFC geographic reporting areas in 2025. Percentages are calculated from each area’s published human and lightning counts.

In Alaska, lightning caused slightly more than half of reported fires but accounted for 99.8% of the area burned. In the Southern Area, it caused 2.8% of fires and accounted for 16.1% of burned area. A national average therefore needs local context before it guides a management plan.

Why keep watching after lightning?

There are practical reasons to watch for fires after lightning. A strike can start a fire in a remote place that is difficult to reach. Some fires then smoulder for days before becoming more visible. These delayed fires are known as holdovers. Research supported by the US National Science Foundation found that lightning-started fires can develop even when a storm brings some rain. The storm passing does not necessarily mean the danger has passed. Read NSF’s explanation of lightning and holdover fires.

The annual totals alone cannot explain why one fire becomes large while another stays small. A 2025 study of historical US Forest Service records found that ignition patterns differed across regions, and that the sources responsible for frequent fires could differ from those associated with the largest burned areas. This supports looking at local causes and conditions together. Read the US Geological Survey research.

Burned area also has limits as a measure of harm. It does not describe losses to homes, disruption to a business or the ecological effects of a fire. Fire can be part of a healthy ecosystem; land managers assess its effects and the threats to people and property when deciding how to respond. Read the US National Park Service’s explanation.

What does this mean for prevention?

For prevention, the large human contribution makes everyday practices worth attention. Maintaining vehicles and equipment, following local restrictions, and ensuring staff and visitors understand campfire and debris-burning rules all address recognised ignition sources. The right priorities depend on which activities actually occur on and around the site. See NIFC’s prevention guidance.

For lightning, preparation includes deciding how remote areas will be monitored after storms. For either cause, an alert needs a practical response: someone to verify the event, establish its location and pass useful information to the appropriate teams. Cameras and sensors can support that process, alongside wider prevention and land-management work. Read the US GAO’s wildfire detection overview.

For organisations managing landscapes or infrastructure, the useful question is which ignition sources are most relevant locally, and where a developing fire could go unnoticed. That is a practical starting point for planning monitoring coverage.