A simple theoretical model for temperature variation of actuation voltage for fixed-fixed beam switches is developed and applied to model capacitive radio frequency microelectromechanical systems switches. Measured data from these switches fit very well with the model over a 120°C operating temperature range, demonstrating an average 0.127V/°C to 0.132V/°C with less than 8% deviation between measured and modeled results. The proposed model provides valuable insight into the factors impacting variability of actuation voltage over broad temperature ranges.