Accurate prediction of atmospheric attenuation is critical for the reliable deployment of Free Space Optical (FSO) communication systems, particularly in regions with diverse climatic conditions. This paper presents a comparative validation of three widely used empirical attenuation models—Kruse, Kim, and Al Naboulsi—using real meteorological visibility data from Nigeria. Visibility records obtained from the Nigerian Meteorological Agency (NiMet) for Lagos, Port Harcourt, Abuja, Jos, and Kano were used to compute attenuation coefficients at an operating wavelength of 1550 nm. Simulation results were compared with attenuation values derived from measured visibility data using correlation and root mean square error (RMSE) metrics. Results show that the Kim model provides the highest correlation (0.93) and lowest RMSE (2.7 dB/km), demonstrating superior suitability for tropical atmospheric conditions. The findings offer validated guidelines for selecting appropriate attenuation models for FSO-based 5G backhaul and last-mile deployments in Nigeria.