Versión casi final TAAC-D-14-00118R2 Temperature determining larger wildland fires in NE Spain JOURNAL: Theoretical and Applied Climatology Temperature determining larger wildland fires in NE Spain D.M.Molina-Terrén 1,*Phone+34 973 70 2847Emaildmolinat@gmail.com A.Cardil 1 1School of Agrifood and Forestry Science and EngineeringUniversity of LleidaAv. Rovira Roure 19125198LleidaSpain Abstract Significant relationships were found between high-temperature days and wildland fire occurrence in the 1978–2011 period in Aragón (NE Spain). Temperature was analyzed at 850 hPa to characterize the low troposphere state, avoiding problems that affect surface reanalysis and providing regional coverage. A high-temperature day was established when air temperature was higher than 20 °C at 850 hPa. The number of these days increased significantly in the study period, increasing the frequency of adverse weather conditions that could facilitate extreme fire behavior. Specifically, these high-temperature days are more frequent in June than they used to be. The effects of those high-temperature days in wildland fire patterns were significant in terms of burned area, number of wildland fires, and average size. Fires larger than 60 ha were the subject of this study. These wildland fires have been increasing in number and size in the last years of the series. Abstract AQ2 1. Introduction Heat waves are usually renowned to damage agriculture, forests, and economic activities and also can play a key role also in terms of human health issues (Kuglitsch et al. 2010; Trigo et al. 2006; Mills 2005). Southern European countries like Spain have many wildland fires each year (Salis et al. 2012; Pereira et al. 2011). Fire has always been part of the traditional Mediterranean agrarian land management, occasionally evolving into unwelcome wildfires (Molina et al. 2010; Millán et al. 1998). Nevertheless, over the past 40 years, wildland fires have turned