The electric field distribution (magnitude only) near a radiating source (antenna) can be easily determined using infrared thermography. A thin screen (made of carbon fiber reinforced polymers) is placed in front of a microwave source. The electromagnetic waves impinging on the screen are partially absorbed, resulting in temperature rise of the screen. This temperature rise is monitored by an infrared camera. The temperature distribution thus observed is mapped to the electric field strength (magnitude of electric field) of the electromagnetic waves. Points on the screen where the temperature rise is low correspond to weak electromagnetic fields whereas points with high temperature rise correspond to strong electromagnetic fields. In this paper electro-thermal modelling is done so as to obtain the temperature distribution over the screen, when an electromagnetic field is incident on it. This model can conversely be used for finding electromagnetic field distributions from IR thermal images. © 2017, Springer Science+Business Media, LLC.