Temperature plays many important roles in the growth and development of cotton. Low temperatures after sowing increase the time to emergence and reduce seedling vigour often leading to poor establishment, poor early growth and increased risk of seedling diseases. The tinting of crop maturity, yield and fibre quality may also be affected. Research is being conducted to improve our understanding of the impacts of temperature extremes on cotton performance. In Australian cotton production systems events where the minimum daily temperature falls below 11'C are referred to as 'cold shocks'. The number of cold shocks is used by growers and advisors in assessing retardation of crops in their areas. However, this effect has not been tested explicitly. The aim of this work was to empirically assess impacts of cold shock on pre flower development of cotton plants. Cotton seedlings were grown in controlled temperature glasshouses. Plants were transferred to cold chambers ranging from 5 to 22'C during the night period for durations from 3 to 10 d. Negative impacts were not seen until plants had been exposed to at least 10 nights at 10&#39C;, or for at least 5 nights at 5'C. When differences were generated it did not delay development to first square any more than 4 d, nor was the effect consistent. These differences translated into delays to first flower. However the delays are explained by the reduction in day degrees during the chilling period suggesting that there is no physiological damage to the plants. Improving understanding of the impacts of temperature extremes on cotton growth and development will help in developing more functional decision support tools and field management strategies