To our knowledge very limited experimental data on the impact of extreme temperatures on corn production is available. These data is specifically relevant to predict the influence of global warming. Sweet corn (Zea mays L.) variety "Silver Queen" were grown in four growth chambers of the Georgia Envirotron for the period of 80 days. Day/night temperatures were 25/20,30/25,35/30 and 40/35 ━C. The envirotrons area was 6.5 m2 and its height was 2.1 m. Incoming and reflected radiation varied between 390 and 460 and between 50 and 80 W m-2 respectively . Inside wind speed was 0.15-0.3 ms-1. A novel device called the PTM-48M, monitored photosynthesis and transpiration. It can automatically measure gas exchange of four individual leaves on a near continuous basis. High temperature inhibited the photosynthetic rate with minimum 10-15 mmol m-2s-1 during the daytime at the 40/35 ━C. Maximum (30-35 mmol m-2 s-1) was measured at the 25/20 treatment. An increase of 15 ━C in temperature was associated with a decrease of 15 mmol m-2 s-1. Transpiration reached 100 mg m-2 s-1 which for the 14 daylight hours is equivalent to 8.4 mm/day. Transpiration occurred also at darkness with a lower limit that varied between 5 and 7 mg m-2 s-1 (0.2-0.25 mm/day) for 10 dark hours. The transpiration coefficient for the 40/35 ━C treatment was about 200 kg-water/kg dry matter assimilation. For the 30/25 ━C it was only 100 units. Results indicated that global warming may be associated with reduction of agroproductivity and crops water use efficiency while increasing water consumption.