Impact of climatic parameters on grain yield of rice cultivars under three dates of transplanting (30th June, 15th July and 30th July) was assessed at Faizabad Uttar Pradesh using calibrated and validated CERES-Rice model by incremental change in climatic parameters. The increase in sunshine duration and solar radiation caused increase in the yield and vice versa, while increase in maximum and minimum temperatures caused decrease in the yield. Among the sowing dates, the impact of sunshine duration under early transplanted rice (30th June) was higher than late transplanted rice (30th July). W hile the reverse trend was observed in case of solar radiation. The effect of maximum and minimum temperatures under early transplanted rice was also higher than that of late transplanted rice.