Measurements of air temperature, water vapour pressure and water vapour deficit were carried out in July and August in the year 2000. Simultaneously, the structure of heat balance of active surface of four agricultural tillages was assessed. Measurements were carried out at the same time over fields of alfalfa, corn, winter and spring wheat. The Bowen method was used to estimate the value of heat balance components. In this paper, the values of abovementioned meteorological compo-nents measured over different plant covers were compared. This comparison was made both for hourly and mean daily values. During the measurement period, mean value of air temperature over wheat field was higher by about 0.31C in relation to air temperature measured over corn field. These differences were bigger on warmer days. Water vapour pressure was higher by about 0.34 hPa over corn field, and water vapour deficit was higher by about 0.75 hPa over wheat field. Differences of hourly and mean daily values of meteorological components reveal statistical dependences on air temperature and it is possible to describe them by means of regression lines. The main reason of observed differences was a dissimilar physiological state of plants of individual tillages. During the measurement period, wheat was rather in the final stage of vegetation. On the other hand, corn was in its full state of vegetation.