MEMS devices are gaining acceptance with many industries, but reliability concerns remain a barrier to entry into many markets. These inherently three-dimensional devices often have considerably more complex production processes and tolerances than standard silicon circuits. In addition, they require characterization not just in a static sense but also during actuation. Previous studies have shown that strobed interferometry is an effective method for complete three dimensional surface characterization of devices moving at frequencies up to 1MHz. To fully characterize MEMS devices, one must also examine the effect of environment on their critical performance parameters. Some devices, such as optical switches, may be subject to high amounts of power during use, and this can deform the devices temporarily or permanently through methods such as crystallization of polysilicon. Also, many devices, particularly for automotive telecommunications, and wireless applications are naturally subjected to a wide variety of environmental conditions. This paper presents measurement results of an optical switch as it is subjected to thermal stresses as an example of environmental characterization using strobed interferometry. A high-power laser is directed onto the device in a configuration equivalent to the desired use condition, and deformation amounts and damage threshold are quantified. Also, the challenges of interferometric dynamic device testing through a cover glass, needed for production characterization, are presented, along with solutions currently in place.