Microwave heating is a very versatile technology that can be used in a wide range of applications, so this question must be answered with respect to categories of applications.
Many industrial microwave systems are used to dry various organic and inorganic materials, or to defrost, cook, or pasteurize food products. This class of applications takes advantage of the fact that microwave heat water molecules much more strongly than most other substances. In general, this means that the material will not get hotter than the boiling point of water. If needed temperature sensors and controls can regulate the exact temperature. This is a good thing for many food products, as excessive temperatures can damage beneficial proteins, enzymes, and other nutrients. This means that microwave processed foods can have better nutritional profiles than convection heated products.
In another class of applications there is little or no water present, so the amount of heating depends solely on the dielectric properties of the materials. An example is heating catalysts for chemical reactions to very high temperatures. In this scenario, the operating temperature can range into the hundreds or even thousands of degrees.
And finally we have microwave induced gas plasmas which can reach many thousands of degrees C. Microwave plasma systems are widely used by the semiconductor industry for deposition systems.
