The Indo-Gangetic plains of India have been experiencing erratic weather and unpredictable rainfall patterns for the past 5 years, the average annual rainfall being 1200–1500 mm in the cropping season. Millets are generally grown in this region during the rainy season but environmental fluctuations result in heavy yield penalties in proso millet. Proso millet is one of the preferred crops of this region; however, it is very prone to yield loss due to flooding. Stability studies were conducted to investigate growing proso millet as a catch crop during summer (February–May) as it is a short-duration crop and can fit well in the existing cropping system. This study aims to determine the effect of genotype, environment and their interaction on grain yield and to identify more stable proso millet genotypes suitable for cultivation in the summer season. In total, 63 genotypes were evaluated for various agro-morphological traits for two summer and one kharif seasons. Stability analysis using a GGE biplot revealed that the proso millet performed better in the summer season than in the kharif season. This study has identified summer season as the most ideal environment for multilocation testing of wining genotypes RAU PM- 17, RAU PM-22, RAU PM-35, RAU PM-54, BR-7, TNAU-202 and TNAU-164 which has high stability for the summer season and can be used in breeding programmes as donor parents for traits like grain yield, 1000 grain weight, panicle length and number of productive tillers.