Methods and systems are provided for conducting measurements of relative humidity via the use of an ultrasonic sensor. In one example, the ultrasonic sensor for conducting the relative humidity measurement is selected from a plurality of ultrasonic sensors positioned at various locations on the vehicle, and where the selecting is accomplished in some examples via the use of one or more onboard cameras configured to identify suitable objects that are stationary with respect to the vehicle. In this way, robustness and accuracy of relative humidity measurements may be improved, lifetime of individual ultrasonic sensors may be extended, and vehicle operating conditions that depend on accurate relative humidity measurements may be improved.