How to read a wildfire map: hotspots, FRP and confidence
Live wildfire maps show what satellites can see. Knowing how to read them avoids two common mistakes: thinking every dot is a wildfire, and believing that no dots means no fire.
1. What a hotspot is
Each dot on the map is a thermal anomaly: an area that was much hotter than its surroundings at the moment the satellite passed over. It can be a wildfire, but also agricultural burning, an industrial facility or, occasionally, a strong reflection of sunlight off a surface.
On incendiohoy.es we group nearby hotspots into a single fire and mark as confirmed those that match a Copernicus EFFIS burnt area or official information, or that combine several detections or a medium-to-high intensity. The details are in our methodology.
2. Which satellites the data comes from
- VIIRS (Suomi NPP, NOAA-20 and NOAA-21 satellites): pixels of about 375 metres, detects smaller fires and locates them more precisely.
- MODIS (Terra and Aqua satellites): pixels of around 1 kilometre and a long data history.
These are polar-orbiting satellites: they pass over Spain a few times a day, mostly in the early hours and around midday or early afternoon. Between passes there is no new data, and NASA usually publishes each detection in less than three hours.
3. Intensity: FRP
FRP (Fire Radiative Power) measures, in megawatts (MW), the energy the hotspot was radiating at the moment of observation. It indicates intensity, not burnt area:
- Below 50 MW: low intensity (agricultural burning, small fires or fires being put out).
- Between 50 and 200 MW: medium intensity.
- Above 200 MW: high intensity, typical of active wildfires.
The same fire can show very different values depending on when the satellite passed, the wind, or which part of the fire front was observed.
4. The confidence level
NASA assigns a confidence level to every detection: low, nominal or high for VIIRS and a percentage for MODIS. Low confidence does not mean there is no fire, but it is worth cross-checking against other detections, satellite imagery or official information.
5. Why a known fire may not appear
- Clouds or very dense smoke hide the fire from the satellite.
- The satellite has not passed over since the fire started.
- The fire is small or low-intensity, or burning under tree cover.
- Detections older than 24 hours are no longer shown as active.
6. Why a hotspot may appear without a fire
- Authorised agricultural burning, common in autumn and winter.
- Industry running at high temperatures (foundries, refineries, gas flares). On incendiohoy.es we filter out hotspots that repeat in the same place on many days.
- Sun glint off roofs, greenhouses or metal surfaces.
7. Approximate position
The dot marks the centre of the satellite pixel, so the fire may be several hundred metres away (up to a kilometre with MODIS) from the exact spot you see on the map. That is why place names are indicative: "near" a municipality.
8. How to get the most out of it
- Use "Are there fires near me?" to see the hotspots closest to your location.
- Open each fire page to see its timeline, its detections and the official sources.
- Check today's fire danger in your province.
- And whenever in doubt or in an emergency, call 112.
Frequently asked questions
How often is the map updated?
We query FIRMS every 5 minutes. New hotspots appear once a satellite has passed over the area and NASA has published its detections, normally in less than three hours.
Does FRP tell me how many hectares have burnt?
No. FRP measures the intensity of the fire at one instant. Burnt area is estimated from Copernicus EFFIS perimeters or comes from the official figures of each autonomous community, usually published days later.
Why do I see hotspots next to factories or near the coast?
Industrial facilities and gas flares emit heat continuously and the satellite detects them just like a fire. Near the coast, pixel position error also plays a part. That is why it is worth checking whether a hotspot is marked as confirmed.
Updated: September 14, 2026 · incendiohoy.es