In our study conducted in north-central Poland in 2001-09 in the lessive soil of a very good rye complex, a relationship between the yielding of tansy phacelia and common sunflower grown as stubble catch crop and the weather conditions that prevailed during the growing period were estimated. The yield of the tested plants grown as stubble catch crop was significantly dependent only on the total precipitation occurring in the period from the beginning of July to the end of August. A good plant supply in water in one of those two months was sufficient to cultivate the catch crop successfully, and optimal total precipitation from the beginning of July to the end of August was 142 mm for tansy phacelia and 150 mm for common sunflower.