Characterizing the interactions between plasma and living organisms has become a multidisciplinary topic in the field of low-temperature plasma science and technology. Living organisms are hierarchically comprised of cells, tissues, organs, and organ systems. Adaptive responses are systematically controlled by the state of the surrounding environment, such as when living organisms are irradiated with discharge plasma. This review is written from a biological perspective and focuses on the importance of gas temperature control in nonequilibrium atmospheric pressure plasmas. We discuss the critical parameters associated with direct plasma treatments of living organisms. This review provides an assessment of the status of this research field and addresses the prospects for further developments in understanding the interactions between plasma and living organisms. We address the importance and necessity of normothermic plasma treatment, where an experimental system involving living organisms is controlled at an optimal temperature, which plays a significant role in plasma biology.