The variation of the air temperature within the Someş – Tisa hydrographic basin during the period 1961 – 2005. This paper analyses the yearly, seasonal and daily variations of the average, minimum and maximum air temperatures, between 1961 – 2005, at 10 meteorological stations from the Someş – Tisa hydrographic basin (7 stations from plane and plateau regions and 3 stations from mountainous regions). The average, maximum and minimum temperatures are characterized by a linearly increasing trend at all the stations within the basin. Three sub-periods can be observed: two periods characterized by an increase of the average temperature values, separated by one period characterized by a decrease of the average temperature values. The last period of growth (the current period) is the most significant one. The highest values of this increasing trend can be observed particularly for the mean maximal temperature and for the mean minimal temperature. Seasonally, the highest values belong to the summer, followed by the winter, while the trends are negative during the autumn. Within the lower altitude regions, the daily variation of the mean temperature’s trend recorded the highest values at 12.00 and 18.00 GMT, while the mountainous regions recorded the highest values at 18.00 GMT and 06.00 GMT. The mean temperature’s increase in the mountainous, plateau and plain regions is due mostly to the increase of the minimum temperatures, and, within the NW region of the basin, to the increase of the maximum temperatures. Local influences can be observed in the case of sheltered depressions (Baia Mare) or in the case of some urban regions with recently developed areas (Bistriţa).