In order to analyze the impairments of Terahertz (THz) and infrared (IR) links caused by attenuation through emulated weather conditions of rain, fog, dust, and air turbulence, THz and IR free-space communication channels at 625 GHz and 1550 nm, respectively, with a maximum data rate of 2.5 Gb/s have been developed in our lab. These two links are spatially superimposed and propagate through exactly the same weather conditions. Various weather emulating chambers were designed that can generate controllable weather conditions. The performance of both channels is analyzed by measuring the power and bit-errorrates (BERs) in each link. Numerical simulations of THz and IR attenuation and link performance under different weather conditions are conducted and compared with experimental results. Under the same weather conditions, the impact of dust, fog, and air turbulence is significantly less on THz links compared to freespace optical links. Under identical rain conditions, the performance of THz and free-space optical links are comparable.