Hi, many researchers have tried to investigate the effects of factors like rain, fog, water vapor etc., especially on mmWave frequencies. 5G/IMT 2020 is using the mmWave/ GHz range of frequencies according to the TS 38.000 specifications.
The free space path loss in radio applications is directly proportional to the square of the frequency, so higher the frequency used, higher will be the resulting loss. Experiments show that compared to the free space pathloss for a given distance at 2.4GHz, the FSPL is about 22dB larger for 28GHz and about 32dB larger for 100GHz.
Recommendation ITU-R P.840-3(2013) discloses the attenuation due to fog/rain increasing considerably with the frequency range increase.