Were used 18 ewes of three different breed group, distributed in a completely randomized design in a factorial diagram (3 x 3, 3 breed group: Santa Inês (SI); ½ Santa Inês + ½ Dorper (Do x SI), and ½ Santa Inês + ½ Texel (Tx x SI) and 3 times of observation: (07:00, 13:00 and 19:00 hours) with 6 repetitions. The aim of this research was to evaluate the physiological responses of Santa Ines and their crossbred with Dorper and Texel breeds to climate conditions of Piracicaba - SP. The variance analysis did not show significant interactions (P>0.05) between the studied factors. It was verified the effect of the breed group to the RT (rectal temperature), ST (skin temperature) and RR (respiratory rate). The SI breed presented RT and RR lower (P<0.05) than the other breed groups. While the Texel presented ST lower and the RR greater (P<0.05) than the other groups. The Dorper presented ST and RR similar to SI, and RT and TT were not different (P>0.05) to the others. There was effect (P<0.05) of the time of observation to the all studied variables. Were registered superior means (P<0.05) to ST, TT and RR at 13:00 o`clock in relation to the other times. To RT there was no difference between the times 13:00 and 19:00, and the means of these times were greater (P<0.05) than that registered at 7:00. It can be concluded that Santa Inês breed should be used in crossbreed with breed with wool to improve the capacity of heat tolerance.