Forest fires represent threat mostly in countries situated in temperate climate zone, however, because of the changing climate, longer periods of high temperatures and drought, we can expect that their number and extent will increase in Slovakia, too. There are several factors influencing the initiation and further propagation of forest fire. Among the most important factors belong the volume and type of fuel available, topography, meteorological conditions and the time of fire. Those influence mostly the fire propagation, i.e. fire behaviour. In the paper, we introduce the results of a study focusing the fire behaviour in changing wind speed conditions. To model the fire behaviour, the FARSITE software was applied. In the modelling, we applied the data on real forest fire that occurred in the Slovensky Raj National Park, Koc locality in 2007. We modelled the fire behaviour for 24 h, using the specific wind speeds (0 km/h, 34 km/h, 68 km/h). According to the modelling results, we analysed the trend of fire propagation for each wind speed and provided the correlation analysis between the fire site extent (fire area and fire perimeter) and wind speed in Statistica 12 software. The fire propagation in time trend analysis results showed, that during the night, the extent of fire site was not increasing, probably because of the lower night temperatures and increasing moisture of the vegetation, over the moisture of extinction critical point, but not because of wind. The process of fire propagation started in the morning, after sun rise, again. The correlation analysis results showed very strong dependency between the fire site extent and wind speed. The results of this study have its immediate utilisation in the fire-fighters practice as for intervention commanders’ decision support as for fire-fighters education and training.