  This paper presents analytical and empirical data documenting the effects of
solar radio emissions on outdoor propagation path loss at 60 GHz bands. Both
line-of-sight (LOS) and non-LOS scenarios were considered. The setup used in
the empirical studies emulates the future fifth-generation cellular systems for
both access and backhaul services, as well as for device-to-device
communications. Based on the measurement data collected in sunny weather with
intense solar activities, we developed large-scale propagation path loss models
at 60 GHz, and observed the effects of solar radio emissions on the path loss
data. It is shown that solar radio emission can decrease carrier-to-noise
ratio, and that this translates into a corresponding increase in the path loss
exponent (PLE) values for the large-scale propagation path loss channel models.
Empirical data show that 9.0%-15.6% higher PLE values were observed in hot and
sunny weather during the day (41{\deg}-42 {\deg}C) compared with the
counterpart measurements taken at night in cool and clear weather (20{\deg}-38
{\deg}C). This translates into a corresponding decrease in 60 GHz radio
coverage in hot and sunny weather during the day. The empirical data are
closely corroborated by analytical estimates presented.
