An autonomous robot apparatus that is activated to perform a work routine upon detecting the accumulation of precipitation. In one aspect, the invention can be an autonomous robot apparatus comprising: a chassis; a plurality of wheels mounted to the chassis; a drive system mounted to the chassis and operably coupled to the plurality of wheels; a control module operably coupled to the drive system; a precipitation sensing module comprising an accumulation level sensor configured to generate and transmit, to the control module, a first signal upon a predetermined initial accumulation level being detected; and the control module configured to activate the autonomous robot apparatus to perform a first instance of a work routine upon receipt of the first signal.