The paper deals with a multiple model of relationships between the yield of alfalfa (var. Kleszczewska) and the weather course that was published in 1987 in Pamiętnik Puławski No. 89. According to the model, total green matter yield from three cuts is affected by:

• thermal and snow conditions in winter (Dec.-Feb.) and in March,
• sunshine and temperature together with rainfall from the start of vegetation until the first harvest,
• date when the plants of the second cut start to re-grow,
• rainfall together with sunshine during the creation of the second cut yield,
• rainfall during the above-mentioned period together with rainfall preceding the harvest of the first cut,
• date when the plants of the third cut start to re-grow,
• rainfall together with sunshine during the creation of the third cut yield.

Insertion of the values of weather elements from the years 1951-1980 into the partial regression models made it possible to determine theoretical yields for 58 sites. Then total yield-creating weather effects were assessed for the multi-year period under study. They were valuation indexes for agroclimate (dt/ha) related to standardized background of agricultural conditions over the years. Application of spatial interpolation allowed to obtain a map of agroclimate for alfalfa production in Poland and a map of yield variation caused by the long-term weather course.