The present disclosure relates to an air temperature regulating device for use in a cargo box to be transported in a vehicle, the cargo box including a wall with a receiving opening, the air temperature regulating device including a portable housing configured to be received in the receiving opening of the cargo box and to be attached to the wall of the cargo box, wherein in the housing are arranged a heat pump, inlets and outlets, wherein the housing includes a head part and neck part adjoining one another, wherein the cross-sectional area of the neck part is smaller than that of the head part to the extent that in attached position the neck part fits within the receiving opening in the wall of the cargo box and the head part covers the circumferential edge of the receiving opening.