{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,2]],"date-time":"2026-03-02T22:51:56Z","timestamp":1772491916017,"version":"3.50.1"},"reference-count":54,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2025,9,4]],"date-time":"2025-09-04T00:00:00Z","timestamp":1756944000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FCT\u2014Portuguese Foundation for Science and Technology","award":["UID\/04033"],"award-info":[{"award-number":["UID\/04033"]}]},{"name":"FCT\u2014Portuguese Foundation for Science and Technology","award":["LA\/P\/0126\/2020"],"award-info":[{"award-number":["LA\/P\/0126\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Forests"],"abstract":"<jats:p>Wildfires in Portugal have become increasingly frequent and severe, driven by a combination of fuel accumulation, extreme meteorological conditions, and topographic complexity. This study assesses the applicability of the Hot\u2013Dry\u2013Windy (HDW) index in characterizing fire-weather conditions during five major wildfires: Chamusca (2003), Pedr\u00f3g\u00e3o Grande and Lous\u00e3 (2017), Monchique (2018), and Covilh\u00e3 (2022). HDW values were computed at sub-daily resolution and compared against a 1991\u20132020 climatology. This study also evaluates the HDW index as a high-resolution fire danger indicator in Portugal and compares it with the traditional FWI using percentile-based climatology. The findings indicate that during 12 and 15 UTC, HDW in the wildfires in Chamusca (2003) and Lous\u00e3 (2017) exceeded 180\u2013370 units, suggesting extreme air conditions driven by hot, dry, and windy weather patterns. These values denoted extremely flammable conditions since they were significantly higher than the 95th percentile. A distinct peak at 15 UTC for Pedr\u00f3g\u00e3o Grande (2017) topped 140 units (&gt;P95), which is consistent with the ignition timing and a rapid beginning spread. A continuous HDW anomaly that peaked above 200 units between 2 August and 5 August preceded the Monchique (2018) event, suggesting extended heat stress and increased wind contribution. While not as severe as in previous instances, HDW at Covilh\u00e3 (2022) was above the 75th percentile in the early afternoon (12\u201318 UTC). Results show that in all cases, HDW values exceeded the 90th and 95th percentiles during the hours of ignition and early fire spread, with the most critical anomalies occurring between 12 UTC and 18 UTC. Spatial analyses revealed regional-scale patterns of HDW exceedance, aligning with observed ignition zones. Comparisons with the Canadian Fire Weather Index (FWI) revealed that while the FWI captured seasonal fuel aridity, the HDW more effectively resolved short-term meteorological extremes, particularly wind and atmospheric dryness. The HDW index was found to identify high-risk conditions even when FWI values were moderate, highlighting its added diagnostic value. These results support the inclusion of HDW in operational fire danger rating systems for Portugal and other Mediterranean countries, where compound fire-weather extremes are becoming more frequent due to climate change.<\/jats:p>","DOI":"10.3390\/f16091417","type":"journal-article","created":{"date-parts":[[2025,9,4]],"date-time":"2025-09-04T15:31:21Z","timestamp":1756999881000},"page":"1417","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Fire Danger Climatology Using the Hot\u2013Dry\u2013Windy Index: Case Studies from Portugal"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6683-1080","authenticated-orcid":false,"given":"Cristina","family":"Andrade","sequence":"first","affiliation":[{"name":"Natural Hazards Research Center (NHRC.ipt), Instituto Polit\u00e9cnico de Tomar, Quinta do Contador, Estrada da Serra, 2300-313 Tomar, Portugal"},{"name":"Centre for the Research and Technology of Agroenvironmental and Biological Sciences (CITAB), Inov4Agro, Universidade de Tr\u00e1s-os-Montes e Alto Douro (UTAD), Quinta de Prados, 5000-801 Vila Real, Portugal"}]},{"given":"Lourdes","family":"Bugalho","sequence":"additional","affiliation":[{"name":"Portuguese Institute of Sea and Atmosphere (IPMA, I.P.), Rua C do Aeroporto, 1749-077 Lisboa, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"328","DOI":"10.1071\/WF07014","article-title":"Fire activity in Portugal and its relationship to weather and the Canadian Fire Weather Index System","volume":"17","author":"Carvalho","year":"2008","journal-title":"Int. J. Wildland Fire"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"185","DOI":"10.1007\/s10584-013-1005-z","article-title":"Forest fire danger projections in the Mediterranean using ENSEMBLES regional climate change scenarios","volume":"122","author":"Bedia","year":"2014","journal-title":"Clim. Chang."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Ruffault, J., Curt, T., Moron, V., Trigo, R.M., Mouillot, F., Koutsias, N., Pimont, F., Martin-StPaul, N., Barbero, R., and Dupuy, J.-L. (2020). Increased Likelihood of Heat-Induced Large Wildfires in the Mediterranean Basin. Sci. Rep., 10.","DOI":"10.1038\/s41598-020-70069-z"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"7537","DOI":"10.1038\/ncomms8537","article-title":"Climate-induced variations in global wildfire danger from 1979 to 2013","volume":"6","author":"Jolly","year":"2015","journal-title":"Nat. Commun."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"847","DOI":"10.5194\/nhess-18-847-2018","article-title":"Extreme wildfire events are linked to global-change-type droughts in the northern Mediterranean","volume":"18","author":"Ruffault","year":"2018","journal-title":"Nat. Hazards Earth Syst. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Turco, M., Jerez, S., Augusto, S., Tar\u00edn-Carrasco, P., Ratola, N., Jim\u00e9nez-Guerrero, P., and Trigo, R.M. (2019). Climate drivers of the 2017 devastating fires in Portugal. Sci. Rep., 9.","DOI":"10.1038\/s41598-019-50281-2"},{"key":"ref_7","unstructured":"Casajus Valles, A., Marin Ferrer, M., Poljan\u0161ek, K., and Clark, I. (2020). Forest Fires in Portugal in 2017. Science for Disaster Risk Management 2020: Acting Today, Protecting Tomorrow, EUR 30183 EN, Publications Office of the European Union."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Andrade, C., and Bugalho, M.N. (2023). Multi-indices diagnosis of the conditions that have led to the two 2017 major wildfires in Portugal. Fire, 6.","DOI":"10.3390\/fire6020056"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Srock, A.F., Charney, J.J., Potter, B.E., and Goodrick, S.L. (2018). The Hot-Dry-Windy Index: A new fire weather index. Atmosphere, 9.","DOI":"10.3390\/atmos9070279"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"McDonald, J.M., Srock, A.F., and Charney, J.J. (2018). Development and Application of a Hot-Dry-Windy Index (HDW) Climatology. Atmosphere, 9.","DOI":"10.3390\/atmos9070285"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"WF24015","DOI":"10.1071\/WF24015","article-title":"Enhanced prediction of extreme fire weather conditions in spring using the Hot-Dry-Windy Index in Alberta, Canada","volume":"33","author":"Elliott","year":"2024","journal-title":"Int. J. Wildland Fire"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"112207","DOI":"10.1016\/j.ecolind.2024.112207","article-title":"Changes in the severity of compound hot-dry-windy events over global land areas","volume":"165","author":"Feng","year":"2024","journal-title":"Ecol. Indic."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1007\/s13595-020-00933-5","article-title":"Climate change impact on future wildfire danger and activity in southern Europe: A review","volume":"77","author":"Dupuy","year":"2020","journal-title":"Ann. For. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1007\/s10584-013-0787-3","article-title":"Robust Projections of Fire Weather Index in the Mediterranean Using Statistical Downscaling","volume":"120","author":"Bedia","year":"2013","journal-title":"Clim. Chang."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"942","DOI":"10.1016\/j.oneear.2024.05.021","article-title":"Changing fire regimes: Ecosystem impacts in a shifting climate","volume":"7","author":"Hantson","year":"2024","journal-title":"One Earth"},{"key":"ref_16","unstructured":"(2025, May 05). ICNF. Available online: https:\/\/fogos.icnf.pt\/sgif2010\/."},{"key":"ref_17","unstructured":"(2025, May 05). ICNF. Available online: http:\/\/www2.icnf.pt\/portal\/florestas\/dfci\/inc\/estat-sgif."},{"key":"ref_18","unstructured":"(2025, May 05). ICNF\u2014Cartografia da \u00c1rea Ardida. Available online: http:\/\/www2.icnf.pt\/portal\/florestas\/dfci\/inc\/mapas."},{"key":"ref_19","unstructured":"Rothermel, R.C. (1972). A Mathematical Model for Predicting Fire Spread in Wildland Fuels, USDA Forest Service. Research Paper INT-115."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Cohen, J.D., and Deeming, J.E. (1985). The National Fire-Danger Rating System: Basic Equations, General Technical Reports INT-84; USDA Forest Service, Intermountain Forest and Range Experiment Station.","DOI":"10.2737\/PSW-GTR-82"},{"key":"ref_21","unstructured":"Fosberg, M.A. (1978, January 19\u201321). Weather in wildland fire management: The Fire Weather Index. Proceedings of the Conference on Sierra Nevada Meteorology of the American Meteorological Society and the USDA Forest Service, South Lake Tahoe, CA, USA."},{"key":"ref_22","first-page":"23","article-title":"A lower atmosphere severity index for wildland fires","volume":"13","author":"Haines","year":"1988","journal-title":"Natl. Weather. Dig."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"109749","DOI":"10.1016\/j.agrformet.2023.109749","article-title":"Changes in European fire weather extremes and related atmospheric drivers","volume":"342","author":"Giannaros","year":"2023","journal-title":"Agric. For. Meteorol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1175\/JAMC-D-17-0167.1","article-title":"Climatological Variability of Fire Weather in Australia","volume":"57","author":"Dowdy","year":"2018","journal-title":"J. App. Meteorol. Clim."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"L10701","DOI":"10.1029\/2005GL022410","article-title":"How exceptional was the early August 2003 heatwave in France?","volume":"32","author":"Trigo","year":"2005","journal-title":"Geophys. Res. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Pereira, M.G., Gon\u00e7alves, N., and Amraoui, M. (2024). The Influence of Wildfire Climate on Wildfire Incidence: The Case of Portugal. Fire, 7.","DOI":"10.20944\/preprints202406.0380.v1"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1016\/j.agrformet.2004.12.007","article-title":"Synoptic patterns associated with large summer forest fires in Portugal","volume":"129","author":"Pereira","year":"2005","journal-title":"Agric. For. Meteorol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1741","DOI":"10.1002\/joc.1333","article-title":"Atmospheric conditions associated with the exceptional fire season of 2003 in Portugal","volume":"26","author":"Trigo","year":"2006","journal-title":"Int. J. Climatol."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Tedim, F., Leone, V., and McGee, T.K. (2020). The role of weather and climate conditions on extreme wildfires. Extreme Wildfire Events and Disasters, Elsevier.","DOI":"10.1016\/B978-0-12-815721-3.00001-1"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"110108","DOI":"10.1016\/j.agrformet.2024.110108","article-title":"Lightning-induced fire regime in Portugal based on satellite-derived and in situ data","volume":"355","author":"Menezes","year":"2024","journal-title":"Agric. For. Meteorol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"74","DOI":"10.3390\/meteorology2010006","article-title":"Changes in the Seasonality of Fire Activity and Fire Weather in Portugal: Is the Wildfire Season Really Longer?","volume":"2","author":"Silva","year":"2023","journal-title":"Meteorology"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Pinto, P., Silva, \u00c1.P., Viegas, D.X., Almeida, M., Raposo, J., and Ribeiro, L.M. (2022). Influence of Convectively Driven Flows in the Course of a Large Fire in Portugal: The Case of Pedr\u00f3g\u00e3o Grande. Atmosphere, 13.","DOI":"10.3390\/atmos13030414"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"107649","DOI":"10.1016\/j.atmosres.2024.107649","article-title":"Atmospheric dynamics and fire-induced phenomena: Insights from a comprehensive analysis of the Sert\u00e3 wildfire event","volume":"310","author":"Menezes","year":"2024","journal-title":"Atmos. Res."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"S49","DOI":"10.1175\/BAMS-D-18-0109.1","article-title":"The Exceptional Summer Heat Wave in Southern Europe 2017","volume":"100","author":"Kew","year":"2019","journal-title":"Bull. Meteorol. Soc."},{"key":"ref_35","unstructured":"IPMA (2017). Boletim Climatol\u00f3gico Maio 2017, IPMA. (In Portuguese)."},{"key":"ref_36","unstructured":"FRAMES Catalog (2025, May 05). Influence of MCS in Pedr\u00f3g\u00e3o Grande Fire Spread. FRAMES 2022, Record No. 65433, Available online: https:\/\/www.frames.gov\/catalog\/65433."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Castellnou, M., Guiomar, N., Rego, F., and Fernandes, P.M. (2018). Fire growth patterns in the 2017 mega fire episode of October 15, central Portugal. Advances in Forest Fire Research 2018, Imprensa da Universidade de Coimbra.","DOI":"10.14195\/978-989-26-16-506_48"},{"key":"ref_38","unstructured":"Thomas, D. (2025, May 05). Five years on \u2026 remembering the fires of October 2017. Portugal Resident, 13 October 2022. Available online: https:\/\/www.portugalresident.com\/five-years-on-remembering-the-fires-of-october-2017\/."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"106141","DOI":"10.1016\/j.isci.2023.106141","article-title":"The compound event that triggered the destructive fires of October 2017 in Portugal","volume":"26","author":"Ramos","year":"2023","journal-title":"iScience"},{"key":"ref_40","unstructured":"Viegas, D.X., Almeida, M.F., and Ribeiro, L.M. (2019). An\u00e1lise dos Inc\u00eandios Florestais Ocorridos a 15 de Outubro de 2017. Centro de Estudos Sobre Inc\u00eandios Florestais ADAI\/LAETA, Universidade de Coimbra."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"106776","DOI":"10.1016\/j.atmosres.2023.106776","article-title":"Modelling pyro-convection phenomenon during a mega-fire event in Portugal","volume":"290","author":"Campos","year":"2023","journal-title":"Atmos. Res."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"107923","DOI":"10.1016\/j.agrformet.2020.107923","article-title":"Recent evolution of spatial and temporal patterns of burnt areas and fire weather risk in the Iberian Peninsula","volume":"287","author":"Calheiros","year":"2020","journal-title":"Agric. For. Meteorol."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Dur\u00e3o, R.M., Alonso, C., and Gouveia, C.M. (2022). The performance of ECMWF Ensemble Prediction System for European extreme fires: Portugal\/Monchique in 2018. Atmosphere, 13.","DOI":"10.3390\/atmos13081239"},{"key":"ref_44","unstructured":"Santos, F.L., Couto, F.T., Salgueiro, V., Potes, M., Jo\u00e3o Costa, M., Bortoli, D., and Salgado, R. (2022, January 23\u201327). Fire weather risk analysis over Portugal in recent decades: Monchique case study. Proceedings of the EGU General Assembly 2022, Vienna, Austria."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"135","DOI":"10.1007\/s40808-025-02308-z","article-title":"Fire-weather conditions during two fires in Southern Portugal: Meteorology, Orography, and Fuel Characteristics","volume":"11","author":"Santos","year":"2025","journal-title":"Model. Earth Syst. Environ."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"3123","DOI":"10.1002\/joc.7411","article-title":"The climatology of extreme wildfires in Portugal, 1980\u20132018: Contributions to forecasting and preparedness","volume":"42","author":"Carmo","year":"2022","journal-title":"Int. J. Climatol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"160320","DOI":"10.1016\/j.scitotenv.2022.160320","article-title":"Drivers and implications of the extreme 2022 wildfire season in Southwest Europe","volume":"59","author":"Rodrigues","year":"2023","journal-title":"Sci. Total Environ."},{"key":"ref_48","unstructured":"Wikipedia contributors (2025, June 10). Grande Inc\u00eandio da Covilh\u00e3 e Crise na Serra da Estrela; Grandes Inc\u00eandios de Portugal de 2022. Available online: https:\/\/pt.wikipedia.org\/wiki\/Grandes_Inc%C3%AAndios_de_Portugal_de_2022."},{"key":"ref_49","unstructured":"Copernicus (2025, May 05). Disastrous Fire in Central Portugal; Copernicus Emergency Management Service. Image of the Day, 17 August 2022. Available online: https:\/\/www.copernicus.eu\/en\/media\/image-day-gallery\/disastrous-fire-central-portugal."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1016\/j.ijgeop.2024.11.005","article-title":"Assessment of forest fires impacts on geoheritage: A study in the Estrela UNESCO Global Geopark, Portugal","volume":"12","author":"Castro","year":"2024","journal-title":"Int. J. Geoherit. Parks"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"2141","DOI":"10.1002\/2016JG003389","article-title":"Characteristics and controls of extremely large wildfires in the western Mediterranean Basin","volume":"121","author":"Fernandes","year":"2016","journal-title":"J. Geophys. Res. Biogeosci."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1038\/s41612-024-00575-8","article-title":"Europe faces up to tenfold increase in extreme fires in a warming climate","volume":"7","author":"Barnard","year":"2024","journal-title":"Npj Clim. Atmos. Sci."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.cliser.2017.04.001","article-title":"Seasonal predictions of Fire Weather Index: Paving the way for their operational applicability in Mediterranean Europe","volume":"9","author":"Bedia","year":"2018","journal-title":"Clim. Serv."},{"key":"ref_54","unstructured":"Van Wagner, C.E., and Pickett, T.L. (1985). Equations and FORTRAN Program for the Canadian Forest Fire Weather Index System, Canadian Forestry Service, Petawawa National Forestry Institute. Forestry Technical Report 33."}],"container-title":["Forests"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4907\/16\/9\/1417\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T18:39:33Z","timestamp":1760035173000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4907\/16\/9\/1417"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,9,4]]},"references-count":54,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2025,9]]}},"alternative-id":["f16091417"],"URL":"https:\/\/doi.org\/10.3390\/f16091417","relation":{},"ISSN":["1999-4907"],"issn-type":[{"value":"1999-4907","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,9,4]]}}}