In this paper the results of the examinations on the effects of various weather conditions on the
development and spatial pattern of the urban heat island (UHI) in Debrecen, Hungary are presented. Measurements
were carried out using mobile technique with instruments that were mounted on cars. Examinations proved the
existence of the UHI in Debrecen. Under favorable weather conditions (anticyclone activity, calm weather) the heat
island showed some unique spatial characteristics. Most regular heat islands developed in cases when Hungary was
situated between weak high and low pressure systems. Under antycyclonic conditions strong heat islands formed, but
their shape was usually deformed by the prevailing winds. Strong cyclone activity eliminated the formation of the
UHI, while under weak cyclone activity regular, but weak heat islands of only about 1°C developed