The dependence of aqueous solution (the NaCl water solution with the salinity 230‰) thermal radiation from the thermodynamic solution temperature was studied. The experiment was performed outdoors in the aqueous solution temperature segment 28–37 ℃. The air temperature in the experiments was -1 ℃. The aqueous solution temperature was measured in the volume of aqueous solution after mixing. A thermocouple was used to receive thermal radiation. The thermocouple was located at a height of 15 cm above the solution level in nadir. The thermocouple signal was recorded when the aqueous solution cooled down. A significantly nonlinear dependence of thermal radiation intensity from the aqueous solution temperature was revealed. The dependence graph contains “valleys” and “peaks” of the aqueous solution radiation. The segments where the thermal radiation of an aqueous solution decreases with an increase in thermodynamic temperature have been identified. The maxima of the dependence of thermal radiation intensity from the aqueous solution temperature in segment 31 and 36 ℃ were revealed. The signal variation was about 20%. It is noted that the appearance of sections with a change in the sign of the derivative qualitatively corresponds to theoretical models.