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Year to year variability in weather poses serious risks to crop production in the environmentally fragile agroecosystems of cool semi-arid areas, and future climate changes might further aggravate those risks. This study aims to quantify the contribution of altered sowing time windows to reduce climate risk for the production of oats (Avena saliva), a crop that is well adapted to short growing seasons and low rainfall. The APSIM-Oats model was calibrated and validated for phenology, above-ground dry matter and yield using data from field experiments with five sowing dates, conducted from 2009 to 2013 in Inner Mongolia, China. The model was used to determine yield trends and yield-limiting factors under rain-fed conditions using historical weather data. Changes in temperature had greater impact on crop production than changes in rainfall and the simulations indicated the importance of changed sowing windows to lengthen the growth duration and optimize water use. Delayed sowing of oats, 10 days later than current practice, ensured more secure temperature and rainfall conditions from emergence to flowering and substantially increased yields and decreased climate risk. Delayed sowing also reduced climate risk under two future climate scenarios, RCP4.5 (stabilize growth) and RCP8.5 (high greenhouse gas emission). We conclude that adaptation of sowing time of oats provides a practical strategy for enhancing yield and mitigating climate risk under climate change.