C otton (Gossypium hirsutum L.) is a direct non-food cash yield of the world, comprehensively utilized in cloth producing industries (Iqbal et al., 2019). Additionally, it is widely used for fiber creation and oil extraction. Pakistan is the fourth in the rundown of significant cotton-producing countries and acquires a Abstract | Temperature is the main climatic factor that influences the yield just as entire development of farming crops. All periods of phenology of crops are temperature sensitive. Hence, information on appropriate temperature for best yield is significant so as to get maximum production. In current examination, a field test was directed to evaluate the phenology, relative development, ideal sowing time, comparative growth just as yield execution of three cultivars of Bacillus thuringiensis Cotton (Bt. Cotton) at different sowing systems during summer 2015 at cotton research station Regional Agriculture Research Institute Bahawalpur (RARI) Pakistan. The test was directed in an irregular complete block design (RCBD) with a split-plot course of action comprising of three replications. One factor comprised of six planting dates (for example April15 and 30, 15 and 30 May, 14 and29 June) and other factor comprising of three Bt. cotton cultivars (BH-184, MNH-886 and CIM-598). The after effects of the test indicated that both sowing dates and cultivars fluctuated fundamentally for development, phenology and yield. Highst leaf area index (LAI) 4.38, total dry matter (TDM) 1033 g m -2 , leaf area duration (LAD) 275.6 days and mean harvest development rate 6.51g m -2 day -1 were recorded on April 30 sowing. Yield contributing boundaries like opened boll, average boll weight and 100-seed weight altogether shifted and highest seed cotton yield 3847 kg ha -1 was acquired by cv. MNH-886 when it was planted on April 30.