An ultrasound apparatus, a medical device comprising such ultrasound apparatus and a method for operating an ultrasound apparatus are proposed. The ultrasound apparatus (10) comprises a power supply (1), system electronics (2) for controlling e.g. at least one of an ultrasound generator and an ultrasound detector , a humidity sensor (5) and a controller (3). The controller (3) is adapted to connect the power supply (1) to the system electronics (2) only in case the humidity sensor (5) detects a humidity below a predetermined threshold. By implementation of such humidity control within the ultrasound apparatus, it can be prevented to operate the ultrasound apparatus under humid conditions which, due to water condensation, may be dangerous for damaging the system electronics (2) of the ultrasound apparatus (10).
