This paper analyses the variation of some physical characteristics of the atmosphere during a 60-year period (1947–2007). The precipitation and temperature data were compared with those of the last decade (1998–2007). The findings suggest that compared with the 60-year period, the last decade witnessed an increase in air temperatures during the vegetation season in West Lithuania. The highest rise in the air temperature (1.1 °C) occurred in July, while the lowest increase (0.3 °C) was recorded in June. During the decade between 1998 and 2007 an increase in the amount of rainfall occurred in June and August (by 12.9–13.4 mm, respectively), and a reduction in May and September (by 8.6–12.7 mm, respectively).

The indicator of the totality of meteorological factors correlates with crop yield during the growing season, this correlation, however, is rather varied. Herbage growth rate and development intensity highly depends on the time of resumption of vegetation. The annual herbage dry matter yield strongly correlates (r = 0.77) with the sum of positive temperatures. In May, the dry matter yield of herbage is most markedly influenced by the warmth, on which duration of herbage re-growth depends (r = 0.88), while in June and July the greatest effect is exerted by rainfall (r = 0.83).

The data from the Vėžaičiai and Vokė weather stations were used for the description of the meteorological conditions.

Keywords: climatic factors, agrocenoses, correlations, the hydrothermal coefficient