Previous research has established that exposure to microwave radiation above a critical level is associated with a reduction across time in the rate at which the energy is absorbed by a mouse. Microwaves caused the animal effectively to decrease the radiation by decreasing the percent absorption of the incident energy. The current investigation sought to determine the effect of ambient temperature on this behavior. Male CFI mice (30 to 34 g) were irradiated by 2450-MHz CW microwaves for 20 minutes in an environmentally controlled waveguide at temperatures of 20, 24, 30, or 35 °C and at a relative humidity of 50±1.5 percent. Forward power in the waveguide ranged from 0.004 to 4 W, which resulted in averaged dose rates of 0.06 to 64 mW/g. When the averaged dose rates were above a critical level, the percent absorption decreased after the initial five minutes of irradiation and remained lower for the duration of the exposure. The threshold level of power at which decreases in percent absorption were observed was found to decrease with an increase in the environmental temperature. The data suggest that the subjects were capable of detecting or otherwise reacting to microwave energy at dose rates as low as 0.6 mW/g when the environmental temperature was 35 °C.