In the present study, six water samples were collected from different locations in the Kingdom of Saudi Arabia and another sample from the Zamzam site in Makkah city. The concentration of the radioactive isotope 222 Rn was measured using the electronic radon detector (RAD7). The comparative analysis study on these samples showed that the average concentration value in all samples was 0.504Bq/L. The data analysis showed that the concentration of 222 Rn was ranged from 0.43 AE 0.06 Bq/L to 0.57 AE 0.060 Bq/L for all samples. These levels are below the contamination threshold (11.1 Bq/L) recommended by the US Environmental Protection Agency (EPA). Interestingly, Radon radioactivity levels were lower than those harmful to human health. The principal component analysis (PCA) using (SPSS version 15) was used to reduce the four variables influencing the 222 Rn activity concentration to two variables: temperature (correlation coefficient, R 2 : 0.984) and the relative humidity (RH%) (R 2 :-0.987). The increase in temperature reduces the solubility of 222 Rn gas activity water and facilitates its detection, whereas increased the RH% increases its solubility and decreases the detection level of 222 Rn activity concentration. The interaction between temperature and RH% does not affect the concentration of 222 Rn.