The influence of temperature on fluorescence spectra used for pressure calibration in a diamond anvil cell (i.e., that of ruby) was always considered as an undesirable phenomenon decreasing the accuracy of pressure measurement in high-temperature experiments. Consequently, nearly temperature-independent fluorescence lines of such pressure calibrants as Sm2+:SrB4O7 and Sm3+:YAG were proposed as the best suited for pressure measurement. We analyzed pressure- and temperature-induced shifts of eight fluorescence lines in Sm2+:SrB4O7 spectrum, extending previous calibrations to 60 GPa and 580 °C, and demonstrated that both pressure and temperature in a "high-pressure + high-temperature" experiment can be reliably estimated by analysis of shifts of two fluorescence lines with different sensitivity to pressure and temperature. We tested the proposed method in an experiment with simultaneous pressure and temperature (up to 7 GPa and 400 °C) and proved that the temperature may be successfully estimated together with pressure from a single Sm2+:SrB4O7 spectrum with an e.s.d. of 8 °C.