Wildland Fire Interagency Geospatial Services (WFIGS) is the interagency group that publishes authoritative map data for U.S. wildland fires under the interagency Wildland Fire Data Program. Its best-known public layers, hosted in the National Interagency Fire Center (NIFC) ArcGIS Online organization, show point locations and the best available perimeters for recent and ongoing fires.
Where the data come from
Incident records come from IRWIN, the Integrated Reporting of Wildland Fire Information integration service. Perimeters are pulled from several sources, with rules that pick the most current or most authoritative shape.
IRWIN holds working data that change as an incident evolves, while final records come later when fire reports are certified. WFIGS uses the certified attributes when they exist and IRWIN for everything else.
What the current layers contain
The current incident locations layer refreshes from IRWIN every 5 minutes and includes wildfires, prescribed fires and incident complexes that have not been declared contained, controlled or out. The current perimeters layer also refreshes every 5 minutes, though a change in the perimeter source can take up to 15 minutes to appear.
Records drop off the current layers when updates stop. A fire under 10 acres falls off after 3 days without an update, a fire of 10 to 100 acres after 8 days, and a larger fire after 14 days.
Separate year-to-date layers keep every perimeter captured for incidents discovered in the current calendar year.
Reading it honestly
A perimeter is the best available mapped shape as of its last update, so the burned area on the ground can differ by the time you see it. Treat it as approximate, especially on a fast-moving fire.
The data's own FAQ says that in most cases, perimeter problems are resolved within a day or two. The license notes the data and graphics are not legal documents.
Where it fits
WFIGS describes fires as agencies have reported and mapped them. Satellite heat detections are a separate, coarser view, and the two are most useful side by side: detections hint at recent heat, and the perimeter shows the reported footprint.