A total of 24 red Angus steers (BW = 431.2 ± 10.4) were used to assess the effect of metabolizable energy intake (MEI) on ADG and tympanic temperature (TT) during summer time in southern Chile. Steers were sorted by BW and allocated in 4 pens (6/pen) equipped with a Calan Broadbent Feeding System, and then allocated into one of 2 treatments 1.85 × or 2.72 × MEI for maintenance. Animals were fed once per day with the same diet, and treatments were applied by controlling DMI. The TT of each steer was collected during 10 d in the summer with an ibutton device. Ambient temperature (AT), relative humidity, wind speed, and solar radiation data were obtained from a weather station near to the farm and used to estimate 2 thermal indices (THI and the Comprehensive Climate Index; CCI). All data were analyzed under a randomized complete block design arrangement (α = 0.05). The mean AT for all the period was 17.2°C. However, there was a great fall of AT (24°C) between day and night. The low temperatures at night allowed for the dissipation of heat accumulated during the day. The steers fed with 1.85 × MEI showed higher TT than those fed with 2.72 × MEI (38.07 vs. 38.02 ± 0.001°C; P < 0.01). However, this difference does not represent a significant change from the biological standpoint. None of the observed thermal comfort indices outperformed the thresholds established in the literature (THI = 68 and CCI = 25). However, maximum values of thermal indices THI, THI_adj and CCI were 75.5, 79.97, and 34.66, respectively. Animals showed signs of thermal discomfort, due to the increase in respiration rate, which was higher by 20 points during the afternoon (P < 0.01). This could be associated with the largest solar radiation received during the afternoon. On the other hand, there were no differences in ADG (1.25 vs. 0.95 ± 0.15 kg/day for 2.72 × and 1.85 × MEI, respectively; P = 0.18). In addition, both values are in line with those projected by the NRC Beef model, with superior value predicted in the case of 1.85 × MEI. Based on the data herein collected we can conclude that for southern Chile, the summer weather conditions and MEI had no effect on productive and physiological responses of animals