One way to develop a cross-curricular lesson is to select the most common mathematical formulas used in science and carefully develop and implement tasks that allow students to make connections between the mathematical representations and theoretical/physical science concepts. The slope-intercept formula, which is used to study relationships between two sets of data, is a fundamental prerequisite concept for understanding scientific phenomenon. The temperature unit conversion formula provides an interesting opportunity to understand the mathematical concept of a linear equation, relate it to the slope-intercept form, and apply the mathematical meaning to the scientific principle. Thermodynamics, the science of heat and temperature, is a central branch of the sciences. Temperature and measurement skills are introduced in elementary school while the Fahrenheit and Celsius conversion formula, which represents the slope-intercept formula, is introduced in middle school and used through graduate-level courses. The activity described in this article is designed to help students understand the temperature unit conversion formula and its relationship to the slope-intercept equation. Skills needed for this activity include graphing calculator skills for entering data, manipulating graphs, and calculating regression equations. The activity focuses on the "Next Generation Science Standards" ("NGSS") practice Using Mathematics and Computational Thinking to develop deeper understanding of scientific formulas and follows the 5E Instructional Model: Engage, Explore, Explain, Elaborate, and Evaluate.