The passive millimeter wave imaging system contains some of the critical electronic circuits which are antenna, low noise amplifier, detector, and low pass filter. This imaging system is connected to the scanning system that can scan between 15.1 degrees and 104.9 degrees in the elevation axis and between -59.9 degrees and -59.9 degrees in the azimuth axis. As a result, the sky temperature can be obtained thanks to elevation axis. The temperature values depend on voltage values because of the system architecture. In this work, the passive millimeter wave imaging system gets the voltage values between 15.1 degrees and 104.9 degrees elevation angles but the analysis is made up to 90 degrees because sky finishes at 90 degrees. There are some obstacles as buildings 70 m away from the scanning system but the distance is enough to measure the sky temperature. After getting the values from the system, the MatLab Computer Program is run according to these values; consequently, voltage-elevation angle graph or temperature (K) x alpha-elevation angle graph is figured out. The experiment were done successfully at 11 a. m. on December 2, 2016 in Umuttepe, Izmit, Kocaeli, Turkey and the weather temperature was 8.7 degrees C (or 305.4 K), and it was also very cloudy.