The thermal difference between the settlements and their environment is called urban heatisland (UHI). Potential UHI intensities are determined by the size, population and built-up structure ofsettlements, while meteorological conditions have a determinant impact on the development of the heatisland at a certain moment. However, not much attention is paid to medium-sized and small towns fromthis aspect in International and Hungarian studies. Consequently, this study has been focused on thedevelopment of UHI in such an environment in Hungary. Settlements, located near the city of Debrecen(cca. 220000 inhabitants) in East Hungary, with population of about 30000, 20000 10000 and 1000 werechosen for the research. Data were collected in two one-year-long mobile measurement campaigns.Spatial characteristics of UHI have been described. Results have proved the existence of UHI even in thesmallest settlement under suitable weather conditions. Effects of cloudiness and wind speed have beenrevealed as well. Stratus clouds have proved to be the most effective in preventing the formation of UHI.Wind speed had a strong impact on the strength of the heat island, while wind directions affected its shapemerely.