Burned area
satellite only112ha
Perimeter published by EFFIS (Copernicus).
- Source
- EFFIS (Copernicus)
- Date
- perimeter revised on 26 January 2022
+− cross-check
No official record is matched to this page to compare it with.
HR · Croatia ·
Grad Slunj fire, 1 March 2021 Grad Slunj
Out · last detection 1 Mar 2021, 12:38 UTC
The fire started on 1 March 2021 in Grad Slunj, Croatia, and satellites saw it burning for 1 day. Copernicus mapped a burnt perimeter of 112 hectares from satellite imagery, spread across a single municipality.
It is the 17th largest in Karlovac since 2016 (of 19 with a page). Number 19 in Croatia in 2021, of 21.
The power measured by the satellite is low (14.8 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
Use this data
Compare with…
Use this data
Fire page data · version 2026-10-24matches the official recordwith caveatssatellite onlymodel
When copying, the sentence is
Tick the figures you want: they make up the lede and the CSV.
Duration by satellite
satellite only1day
1 Mar 2021 to 1 Mar 2021: first and last day with fire on the page.
- Source
- EFFIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- last detection: 1 Mar 2021, 12:38 UTC
+− cross-check
Satellites pass a few times a day and cloud or smoke can hide the fire: a lack of detections is not an official extinction. Each country’s emergency service declares a fire contained or out.
Start
satellite only1 Mar 2021
First day with fire seen by the satellites or the perimeter.
- Source
- EFFIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- 1 Mar 2021
+− cross-check
No official record is matched to this page, so the alert time and the cause are not known here.
Hotspots
satellite only7
VIIRS detections at 375 m. Most intense hotspot: 15 MW.
- Source
- NASA FIRMS · VIIRS (Suomi NPP)
- Date
- 1 Mar 2021 – 1 Mar 2021
+− cross-check
There is no official record to compare with. Each hotspot is a pixel detected in one satellite pass, not a separate fire.
The worst day
satellite only59MW
Total radiative power on 1 March 2021; hotspots that day: 7.
- Source
- NASA FIRMS · VIIRS (FRP)
- Date
- 1 Mar 2021
+− cross-check
Fire radiative power (FRP) measures the energy the fire gives off when the satellite passes. Added up by day, it compares intensity, not area.
Danger at the start
model4.5FWI · very low
Fire Weather Index (Canadian system) computed by WorldFires for the day the fire started. Consecutive days without rain before: 17.
- Source
- WorldFires calculation (Canadian FWI system)
- Date
- 1 Mar 2021, local noon
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
This is an index computed from weather model data, not a measurement of the fire nor an official warning. Danger warnings are issued by each country’s authority. Emergency number and official warnings
Weather during the fire
model12.4°C · 43% RH
High of 12.4 °C and minimum humidity of 43% on 1 March 2021; gusts of 29 km/h on 1 March 2021.
- Source
- weather model at the fire’s grid cell
- Date
- 1 Mar 2021 – 1 Mar 2021
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
These are model values for a cell of about 25 km, not from a weather station: they may differ from what was measured on the ground.
This page’s change log has been kept since 24 October 2026: every night what it publishes is compared and the difference is logged. Anything earlier is reconstructed from each source’s date and marked as reconstructed.
Show
-
· reconstructed weatherWeather and FWI computed from the ERA5 reanalysis
-
· reconstructed perimeterEFFIS (Copernicus) revises the perimeter
What was saved on 24 October 2026
Every night a snapshot of what the page shows is saved. If anything changes, it appears in the list as a log entry.
- Area
- 112 ha
- Dates
- 1 Mar 2021 – 1 Mar 2021
- Name
- Grad Slunj
- Official record
- —
Versioned permanent link
https://worldfires.org/en/fire/grad-slunj-2021-03?v=2026-10-24A version keeps the area, dates, name and official record; the area as it was logged (changes under 2% are not logged). The map, hotspots and weather always show today’s data.
Citation
A lede of about 60 words figures only, no adjectives
CSV for this fire grad-slunj-2021-03.csv · daily, no individual hotspots
| fecha | focos_viirs | frp_mw | tmax_c | tmin_c | hr_min_pct | viento_max_kmh | racha_max_kmh | precip_mm | fwi | clase_fwi | dentro_del_incendio |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2021-03-01 | 7 | 59 | 12.4 | -0.3 | 43 | 10.3 | 29.2 | 0 | 4.5 | muy_bajo | 1 |
| 2021-03-02 | 0 | 0 | 14.2 | 0.2 | 37 | 8.2 | 25.9 | 0 | 4.5 | muy_bajo | 0 |
| 2021-03-03 | 0 | 0 | 18.1 | -0.8 | 24 | 6.9 | 16.9 | 0 | 6.3 | bajo | 0 |
| 2021-03-04 | 0 | 0 | 16.9 | 0.1 | 29 | 13.6 | 40.3 | 0 | 8.4 | bajo | 0 |
| 2021-03-05 | 0 | 0 | 14.2 | 4.2 | 49 | 16.9 | 44.3 | 5.5 | 0.4 | muy_bajo | 0 |
It is generated in your browser from this page’s data: one file per fire, aggregated by day and without individual hotspots.
Live widget for your story
It updates itself while the fire is still active and links to this page. Free, with the attribution shown at the bottom.
Sources for this page: EFFIS (Copernicus), NASA FIRMS (VIIRS), ERA5 (ECMWF/Copernicus C3S) · Open-Meteo.com (CC BY 4.0). Open-Meteo.com · How we build fire pages: methodology
- Burnt area
- 112ha
- Copernicus perimeter
- Duration
- 1day
- 1 Mar 2021 – 1 Mar 2021
- Municipalities hit
- 1
- municipalities
- Started on
- 1 Mar
- 2021
- Heat detections
- 7
- in a single hotspot: 15 MW
- Danger at start
- 4
- Very low · FWI index
- Average daily power
- 59MW
- detected power per day, on average
Where it burned
HOTSPOTS BY DAY
1 Mar1 Mar
How it evolved, day by day
1 Mar 2021 · 59 MW · 7
Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.
The weather it burned in
12°high
29km/h · peak gust
43%lowest humidity
It had gone 17 days without rain (1 mm or more) when it started. Rain came after the fire: 5.5 mm on 5 Mar.
This area had burned before
74% of the perimeter overlaps earlier fires recorded since 2016: 35 ha in 2017, 55 ha in 2020. Part of it burned more than once, so the yearly figures add up to more than the 83 ha that had burned before.
What happened to each town
-
Grad Slunj where it started112 ha reached on 1 Mar0.3 %
Burnt area inside each municipality, from crossing the official perimeter with administrative boundaries. The distance runs from the point marking the centre of each area to the nearest fire: staying a kilometre away does not mean it reached the houses.
What burned
- Scrub and transitional woodland61 %
- Artificial surfaces38 %
- Broadleaved forest0.9 %
Land cover inside the perimeter according to Corine Land Cover, as reported by Copernicus.
The weather day by day
ECMWF ERA5 reanalysis at the fire location, the standard reference for past weather, and the Canadian Fire Weather Index (the same system Copernicus uses), computed by WorldFires from that data. Days after the fire run until the first rain.
Open-Meteo.com (CC BY 4.0) · Copernicus Climate Change Service (ERA5)
| Day | High | Min. humidity | Peak gust | Rain | Danger (FWI) |
|---|---|---|---|---|---|
| 1 Mar | 12.4 °C | 43 % | 29 km/h | 0.0 mm | Very low 4 |
| 2 Mar after | 14.2 °C | 37 % | 26 km/h | 0.0 mm | Very low 4 |
| 3 Mar after | 18.1 °C | 24 % | 17 km/h | 0.0 mm | Low 6 |
| 4 Mar after | 16.9 °C | 29 % | 40 km/h | 0.0 mm | Low 8 |
| 5 Mar after | 14.2 °C | 49 % | 44 km/h | 5.5 mm | Very low 0 |
Its twins: fires that started in the same weather
It started with an FWI of 4.5, a minimum humidity of 43% and 17 days without rain. Fires in the area that started in weather like this since 2016: 16.
FWI at the start
4.5
Minimum humidity
43 %
Days without rain
17
this fire
chosen twins
rest of the area
Almost identicalSimilar
Outlines of the closest twins
This fire · Grad Slunj fire, 1 March 2021
112 ha
1 day
FWI 4.5
Min. humidity 43 %
Bosansko Grahovo fire, March 2017
726 ha
3 days
FWI 4.2
Min. humidity 43 %
131 km away, in 2017
First rain (1 mm or more) after it ended: 4.1 mm on 26 Mar.
Općina Muć fire, March 2022
2,304 ha
11 days
FWI 3.3
Min. humidity 43 %
164 km away, in 2022
First rain (1 mm or more) after it ended: 11.5 mm on 30 Mar.
Grad Gospić fire, March 2017
185 ha
1 day
FWI 6.0
Min. humidity 44 %
72 km away, in 2017
First rain (1 mm or more) after it ended: 4.5 mm on 26 Mar.
Bosansko Grahovo fire, March 2017
244 ha
1 day
FWI 4.9
Min. humidity 44 %
134 km away, in 2017
First rain (1 mm or more) after it ended: 4.1 mm on 26 Mar.
Općina Brinje fire, February 2026
118 ha
2 days
FWI 2.5
Min. humidity 44 %
17 km away, in 2026
First rain (1 mm or more) after it ended: 1.0 mm on 11 Mar.
What happened to them
- 2 days
- median duration
- 230 ha
- median area
- 12 %
- went past 1,000 ha
- 4.4 mm
- rain at the end (median; 16 of 16 had it)
It stayed below its twins: 112 ha against a median of 230 ha. It lasted 1 day, against 2 days.
All of them had rain in the ten days after the end: the first rainy day brought a median of 4.4 mm.
This is a bank of analogues: it shows what usually happens, not what will happen. With fewer than 15 twins we give no figures. How we calculate it
How it ended
5.5 mmfirst rain
5 Mar4 days after it ended
29km/h · max. gust
It was considered over on 1 Mar, and on 5 Mar 5.5 mm fell. We do not know whether the rain or the firefighters put it out. Twins with rain when they ended: 16 of 16, with a median of 4.4 mm.
Weather on this page: Open-Meteo.com (CC BY 4.0) · Copernicus Climate Change Service (ERA5)
How a twin is chosen
- Same area: fires that have already ended, less than 250 km from this one, since 2016.
- Same start: we compare the FWI on the first day, the minimum humidity that day and the run of days without rain before it. The slider sets how much they may differ.
- Only pages with final weather data (ERA5 reanalysis) calculated in the same way as this fire’s; agricultural and grass burns and pages with data under review are left out.
- Fires burning at the same time as this one (a week before or after) are left out: they share the same spell of weather and do not count as a precedent.
- They are sorted by similarity, and the outlines of the first five are drawn.
Before and after, from space
Drag the line to compare the same ground before the fire and after it.
↔
Before · 22 Feb 2021
After · 8 Mar 2021
Sentinel-2 did not pass over on that day. Try another date, or use false colour, which is daily.
If the day is cloudy, change the date: each satellite passes once a day. In false colour the burnt ground looks brown or red.
The smoke
CAMS · CopernicusOn 27 February 2021 the air beside the fire reached 38 µg/m³ of PM2.5. That day averaged 23: 1.5 times the WHO daily guideline (15).
PM2.5 peak38 µg/m³
Days over the guideline3 days
PM1050 µg/m³
WHO 15
27 Feb1 Mar3 Mar
Good
Fair
Moderate
Poor
Very poor
Extremely poor
Particles from the Copernicus CAMS model at the centre of the perimeter; these are not measurements in each town. The pale bar is the worst hour, the solid one the daily average.
Open-Meteo.com (CC BY 4.0) · Copernicus Atmosphere Monitoring Service (CAMS)
Detections table · 7Every satellite heat detection, one by one, with time, satellite, power and coordinates.
⬇ Download CSV
Times in UTC. Each detection is a 375 m pixel: a large fire yields hundreds per pass.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 533 haGrad SlunjFebruary 2020 · 4 days · 8 km away
- 623 haGrad Slunj24 March 2022 · 2 days · 15 km away
- 636 haGrad Slunj4 March 2021 · 2 days · 17 km away
- 454 haGrad Otočac22 March 2022 · 6 days · 26 km away
- 637 haOpćina BarilovićMarch 2022 · 1 day · 28 km away
- 520 haBihaćFebruary 2019 · 4 days · 29 km away
Frequently asked questions
- How long did the Grad Slunj fire last?
- Copernicus dates it between 1 March 2021 and 1 March 2021: 1 day between the first and last image with fire.
- How much area did it burn?
- The perimeter Copernicus measured from satellite imagery is 112 hectares (1.1 km²). Official national figures may differ.
- Which municipalities burned?
- The fire only entered Grad Slunj (112 ha, 0.3 %).
- What was the weather like?
- During the fire the temperature reached 12.4 °C, humidity dropped to 43 % and gusts hit 29 km/h. The fire danger index (FWI) reached 4, class Very low.
- Where does this data come from?
- From the EFFIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Croatia (geoBoundaries). It is not an official report.
- How did the fires that started in similar weather in this area end?
- Fires less than 250 km away that started since 2016 with a similar FWI, humidity and dry spell: 16. Their median duration was 2 days and their median area 230 ha; 12 % went past 1,000 ha. All of them had rain in the ten days after the end: the first rainy day brought a median of 4.4 mm.
Where to verify it
A satellite detection is not an official report. Final figures and the fire’s status are published by each country’s emergency service.
Emergency number: 112 · 193 · Emergency number and official warnings
Satellite cross-check
History of this page Changes in area, dates, name, official record or merged pages, compared every night since 24 October 2026.
No changes since 24 October 2026.
RSS Changes to this page With cross-checks and a citable version
Does something look wrong on this page?
This page is built from satellite data and official records, and it sometimes gets things wrong: the wrong dates, the wrong town, two fires merged into one, or something that was not a wildfire at all. If you know this fire first-hand (you live nearby, saw it, fought it or reported on it), tell us what really happened and we will check it.
Report an error
How we know this
- Perimeter: EFFIS (Copernicus), mapped on satellite imagery.
- Dates from the perimeter: the VIIRS detections inside it did not change them. 7 Suomi-NPP VIIRS detections on those dates.
- We have not matched this page with any official record.
- Weather: Copernicus ERA5 reanalysis at the fire location, in cells of about 25 km.
Where this data comes from
The perimeter and land cover come from the Copernicus European Forest Fire Information System (EFFIS), measured on MODIS and Sentinel-2 imagery and published under CC BY 4.0. Heat detections come from the VIIRS sensors aboard Suomi-NPP and NOAA-20, distributed by NASA FIRMS at 375 m resolution. Municipal boundaries come from geoBoundaries ADM2 (Creative Commons Attribution-ShareAlike 2.0). The area per municipality is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ slightly from each country’s official figure.