Thermography emerged as a practical tool to teach plant biology in higher education. Indeed, thermography can help to teach basic principles of plants' physiology such as their energy balance. The well-established fact that increased leaf temperature reflects stomatal closure, being therefore a measure of plants' response to drought, supports the relevance of the technique. Nowadays, affordable thermographic cameras allow to extend the use of this technology to secondary education. To achieve this goal, however, training high school science teachers is instrumental. We herein report and discuss a training action on the principles of thermography and their application to plant biology.