An environmental test enclosure for modifying the temperature of a vehicle test property is presented. The enclosure includes a movable pallet assembly that is operable to deliver the test property to and from the property test site. The movable pallet assembly includes a base plate that is configured to attach to and support the test property thereon. A plurality of sidewalls project upward from the base plate to surround the test property. A flexible cover is mounted to the overhead structure of the test site, and configured to transition between an open position, in which the cover is in a raised and generally folded state, to a closed position, in which the cover is in a lowered state and attachable to the pallet assembly. The flexible cover cooperates with the movable pallet assembly when attached thereto to define an enclosed and substantially thermally insulated space around the test property.