We have studied the locally released early-season melon varieties (cv. Anush), cucumber (cv. Maneh), and marrow squash (cv. Anna) under the conditions of Ararat valley to assess the influence of meteorological conditions on the development rates and productivity of the summer and spring-planted vegetable plants. Research has been conducted on the experimental field of the Scientific Center of Vegetable, Melon and Industrial Crops (2011-2013). Depending on the seeding time (spring or summer), the tested varieties varied in the durations of germination, blooming and fruit formation periods as well as in  the plant resistance to low and high temperatures in spring and summer, respectively. It was found that, the summer-planted cucurbits crops have significantly shorter plant development phenological phases and prolonged fruit-bearing periods as compared to the spring-planted plants. It was proved for cucumber and marrow squash crops. The yields of the spring-planted melon, cucumber and marrow squash crops were 30,5; 24,8 and 42,5 t/ha, respectively, while the yields of the summer-planted crops were lower (39,9; 7,8 and 8,6%).