Stimulated Brillouin scattering (SBS) in gas-filled hollow-core fibers (HCFs) provides high gain and narrow linewidth, making it a promising platform for advanced photonic applications. While Brillouin gain is known to depend quadratically on pressure and linewidth inversely on pressure, the combined effect of pressure and temperature - through their influence on gas density-has not been fully explored. In this study, we demonstrate that lowering the gas temperature from 373.15 K to 233.15 K at a pressure of 100 bars (using nitrogen) leads to a six-fold increase in Brillouin gain and a twofold reduction in linewidth. We systematically investigate the temperature dependence of key Brillouin parameters, including gain, frequency shift, linewidth, acoustic velocity, and temperature sensitivity, in nitrogen and carbon dioxide gases. The results reveal distinct temperature-dependent behaviors, aligning well with theoretical predictions, and provide new insights, to the best of our knowledge, into optimizing SBS performance in gas-filled hollow-core fibers.