In order that non destructive testing methods become quantitative tools for structure owners, it is needed to assess their precision and sensitivity to the environment. The presented study deals with two electromagnetic methods classically used to survey road pavements and concrete structures: a radar technique and a capacitive technique. The presented investigations aim at assessing the influence of temperature and moisture on the two methods for measurements realized on concrete slabs. The temperature was ranging from 5°C to 45 °C and the surrounding relative humidity (RH) evolved between 60% and 90%. The study is part of a more ambitious topic aiming at defining quantitative non destructive methods to evaluate the water content of concrete structures on site and their state of degradation. The presented work allows assessing the sensitivity of both radar and capacitive techniques to the environmental conditions: temperature and relative humidity. Moreover, the measurement variability of the used capacitive probes with three different sets of electrodes is estimated.