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California Wildfire Activity: A Historical Overview

This interface presents historical wildfire incidents in California for public understanding. It is not intended for real-time decision-making or emergency response.

Project context

Audience

Public, policy, and research audiences

Objective

To support careful understanding of historical wildfire activity and reduce misinterpretation of reported data

Scope

Historical data only; not intended for real-time or operational use

How to read this data

  • Trends reflect reported incidents, not necessarily actual fire occurrence
  • A small number of large fires account for most total acreage burned
  • Differences across regions may reflect variations in reporting and data completeness, not just actual wildfire activity.

Data lineage

This section shows how source wildfire records are transformed into the visuals on this page.

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Step 1

Data source

  • U.S. Forest Service FPA-FOD v6 (1992–2020), provided in this project as raw source input.
  • Field definitions are documented in the Variable descriptions table.
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Step 2

Raw data fields used

  • Incident ID, fire name, year, county/FIPS, cause, acres, latitude, longitude, and discovery timing fields.
  • These fields are selected because they support trend, map, county, and table views.
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Step 3

Data preparation and cleaning

  • Records are scoped to California and historical years (1992–2020).
  • County names/FIPS and cause labels are standardized; missing text is normalized.
  • Invalid coordinates, negative acres, and duplicate records are removed or corrected.
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Step 4

Transformations applied

  • Incidents are sampled for responsive interaction and written to a compact JSON file.
  • Monthly/yearly aggregates, county summaries, and largest-incident slices are generated.
  • Sorting and ranking are used for table order and concentration analysis.
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Step 5

Derived analytical layers

  • KPI totals (fires, acres, average size), monthly trend lines, and county choropleth metrics.
  • Map markers represent ignition-point locations from records, not full burned extent/perimeter.
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Step 6

Filtering logic (including Top 5% mode)

  • All views share the same year, county, and cause filters.
  • Top 5% mode isolates the largest incidents (by acres) within the current filtered subset.
  • Map and table update together so comparisons remain consistent.
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Step 7

Important limitations

  • Reporting consistency differs across agencies and years, so trends can reflect reporting practices.
  • Some records contain missing, uncertain, or revised values.
  • This is historical reporting data for analysis and communication, not real-time operational guidance.

Filter historical data

Refine the year range, counties, and causes to adjust all views below.

Year range

Total Fires

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Total Acres Burned

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Avg. Fire Size (acres)

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A key pattern in wildfire impact

Most wildfire incidents are small in size, but a small number of large fires account for the majority of total area burned.

Wildfire patterns across time and geography

Historical reported wildfire incidents data (1992–2020)

Data may include revisions or incomplete records.

Reported Wildfire Incidents Over Time

Changes may reflect reporting practices as well as real-world activity.

Trend guidance: Use the chart controls on the top-right to switch between Fires-only, Acres-only, and Compare both views so you can inspect each pattern independently or side-by-side.

Drag to set year range:

2015
2016
2017
2018
2019
2020

Where does the burned area actually come from?

Most wildfire acreage is driven by a small number of very large fires. This view shows how much of the total area is contributed by the largest incidents.

This shows that wildfire impact is highly concentrated: a small number of large fires account for most of the total area burned.

Focus filter for largest fires

Top 5%

Use this view to isolate the 1 largest incidents that drive most burned acreage.

How to interpret responsibly

  • Do: Use this data to understand broad historical patterns in wildfire activity
  • Do not: Use this interface for prediction or operational decision-making
  • Do: Recognize that a small number of large fires can dominate total acreage
  • Do not: Assume reported trends directly reflect real-world fire occurrence

Incident-level data

Values may include missing or updated records.

Incident records (all rows by current sort)

Navigation guidance: Select an incident row below to return to the map, center and zoom to that incident, and open the corresponding record details.

Name Year County Cause Acres ▼

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Values may include missing or updated records.

Data & methodology

Source

US Forest Service FPA-FOD v6 (1992–2020), filtered to California

Data provenance

  • Dataset version: US Forest Service FPA-FOD v6 (1992–2020)
  • Last updated: April 17, 2026
  • Preprocessing: Standardized county names, simplified cause categories, and addressed missing values to improve consistency.

Interface

Interactive dashboard to explore historical wildfire activity across California. The map shows ignition locations, where circle size represents acres burned and color represents cause. The dashboard also includes a monthly trend and a sortable incidents table.

Processing

  • Filtered to California incidents
  • Preprocessed into compact JSON
  • Standardized county names (for example “053” → “Monterey”)
  • Standardized wildfire cause categories to ensure consistency across records
  • Filled missing values such as:
    • fire_name → “Unnamed Fire”
    • county → “Unknown”

Scope

Historical wildfire incident data only; not intended for real-time use