Turbulent environment can highly affect the performance of free space optical (FSO) communication links. In order to investigate turbulence effects through an FSO link, an experimental investigation is carried out. Turbulence is measured for a 220 m FSO link in different conditions including temperature of environment, and the time of the day. It is shown that the probability density function (PDF) of the normalized received signal is fitted with the lognormal model. Furthermore, the refractive index structure parameter C _n ² is measured to demonstrate the changes in turbulence during day and night times. The results show that the time of the day and temperature have the biggest effect on C _n ² .