Wildfire Frequently Asked Questions

NearbyFires refreshes NASA FIRMS active fire detection data every 30 minutes. Individual satellites pass overhead every few hours, so the effective update interval for any given point on the ground is driven by satellite overpass timing. Terra and Aqua (MODIS) each pass twice a day; NOAA-20 and Suomi NPP (VIIRS) add additional overpasses.

Small fires under half an acre may fall below the detection threshold of MODIS (1km pixel) and VIIRS (375m pixel). Thick smoke clouds or heavy tree canopy can also obscure a fire from satellite view. Fires that started in the last 1 to 3 hours may not yet have been observed by an overhead satellite. For breaking fires, always check your local fire agency directly.

Containment percentage is the fraction of a fire's perimeter that has a completed control line (fireline, road, river, or other fuel break). A fire at 100% containment may still have active burning inside the perimeter — it is simply not expected to spread further. Containment does not equal "out". See the glossary for full definitions.

FRP measures how much radiant energy a fire is releasing, expressed in megawatts (MW). Higher FRP indicates more intense fire behavior. Typical values range from under 10 MW for small agricultural burns to over 1,000 MW for extreme wildfire behavior. The detection dots on the map are sized by FRP — larger dots mean more intense burning.

MODIS (aboard Terra and Aqua) detects fires at 1km pixel resolution. VIIRS (aboard NOAA-20 and Suomi NPP) detects at 375m — about a 7× smaller footprint. VIIRS picks up smaller fires that MODIS may miss and produces sharper edges. When you see a cluster of VIIRS detections and a single MODIS detection in the same area, it typically represents the same fire observed at different resolutions.

Color indicates the confidence of the detection. Red dots are high-confidence detections (almost certainly active fire). Orange dots are nominal confidence (very likely fire but could include hot industrial sites). Yellow dots are low confidence (includes potential false alarms from sun glint, volcanic activity, or geothermal surfaces). Dot size indicates Fire Radiative Power.

No. NearbyFires is an informational site. For evacuation orders, road closures, and emergency alerts, always check your county Office of Emergency Services, CAL FIRE (California), or your state equivalent agency. Fire detections on this site have inherent satellite latency.

Traditional US wildfire season ran from late May through September, peaking in August. In recent years the season has lengthened substantially — large fires now occur in every month of the year. Winter fires in California such as the December 2017 Thomas Fire and January 2025 Palisades Fire demonstrate the shift toward year-round fire potential. See our annual season recaps for year-by-year patterns.

A wildfire is an unplanned fire burning in wildland fuels. A prescribed burn is an intentional, planned fire set under specific weather and fuel conditions to reduce hazardous fuel buildup, improve wildlife habitat, or maintain ecosystem health. Both can show up as FIRMS satellite detections, which is one reason a detection alone does not equal an emergency.

Visit the states index and select your state. Each state page lists the largest recorded named fires, annual season totals, and county-level fire history. For national records, see the named fires index which ranks the largest US wildfires on record.