An electronics cabinet for storing a plurality of electronic devices therein is provided and includes a fan and an evaporative cooler. The fan draws a flow of air into the cabinet, circulates the flow of air through the evaporative cooler, and then across the electronic devices for removing heat produced by the electronic devices. The evaporative cooler removes heat from the flow of air by absorbing heat from the flow of air and then dissipating the heat by evaporating a liquid into a secondary airflow, which is directed out of the cabinet. The cabinet includes a cold air plenum having an actuator for adjusting a cross-sectional area of the cold air plenum to control the airflow through each of the supports.