For practical applications, the performance of the system should be studied under outdoor conditions. To make the study and the analysis more realistic and extensive, the wind velocity and ambient temperature variations should be considered. It is useful to verify the system performance under these real outdoor conditions if there a wide changing in their values throughout the day. So, in this paper at studying the thermal analysis of the Compound Parabolic Concentrator (CPC) system, these parameters are dealt as varied values in a day depending on an actual data. Numerical calculation is used to study the effects of outdoor conditions on the performance of non-evacuated CPC solar collector at unsteady state, for different values of flow rate. The effect of varying ambient temperature and wind velocity on the system efficiency, temperature of components, heat losses and heat gain at different flow rates are studied and presented graphically. Simulation results demonstrate that, the wind velocity has considerable effects on the cover heat losses, while, the ambient temperature is less effected. However, there are slight effects on the heat gain will be caused by variation in wind velocity and ambient temperature. Therefore the efficiency will be a slightly changed with these parameters. On the other hand, considering the value of outdoor wind velocity as a mean value throughout the day, given sensible results as that which getting from the actual distribution. Whilst, the dealing with the mean value of the ambient temperature obtains some differences.