An ultrasonic surgical instrument, comprising: (a) an end effector configured to actuate from a first configuration to a second configuration, including: (i) an ultrasonic blade configured to selectively apply ultrasonic energy to tissue, and (ii) a jaw movably positioned relative to the ultrasonic blade and configured to move between an open position and a closed position, wherein the jaw and ultrasonic blade in the open position are configured to receive tissue, and wherein the jaw and ultrasonic blade in the closed position are configured to clamp the tissue; (b) a shaft assembly projecting proximally from the end effector; (c) a body projecting proximally from the shaft assembly, wherein the body includes an energy input operatively connected to the ultrasonic blade; and (d) a controller operatively connected to the ultrasonic blade, wherein the controller has a memory including a plurality of predetermined data correlations that correlate changes in measured ultrasonic frequency of the ultrasonic blade to a blade temperature of the ultrasonic blade, wherein the controller is configured to: measure a first ultrasonic frequency of the ultrasonic blade; measure a second ultrasonic frequency of the ultrasonic blade after measuring the first ultrasonic frequency; calculate a frequency parameter change between the measured first and second ultrasonic frequencies of the ultrasonic blade; correlate the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade based on the plurality of predetermined data correlations to thereby determine the temperature of the ultrasonic blade; and adjust at least one power parameter of the ultrasonic energy to limit the blade temperature to an upper temperature limit. (a) an end effector configured to actuate from a first configuration to a second configuration, including: (i) an ultrasonic blade configured to selectively apply ultrasonic energy to tissue, and (ii) a jaw movably positioned relative to the ultrasonic blade and configured to move between an open position and a closed position, wherein the jaw and ultrasonic blade in the open position are configured to receive tissue, and wherein the jaw and ultrasonic blade in the closed position are configured to clamp the tissue; (i) an ultrasonic blade configured to selectively apply ultrasonic energy to tissue, and (ii) a jaw movably positioned relative to the ultrasonic blade and configured to move between an open position and a closed position, wherein the jaw and ultrasonic blade in the open position are configured to receive tissue, and wherein the jaw and ultrasonic blade in the closed position are configured to clamp the tissue; (b) a shaft assembly projecting proximally from the end effector; (c) a body projecting proximally from the shaft assembly, wherein the body includes an energy input operatively connected to the ultrasonic blade; and (d) a controller operatively connected to the ultrasonic blade, wherein the controller has a memory including a plurality of predetermined data correlations that correlate changes in measured ultrasonic frequency of the ultrasonic blade to a blade temperature of the ultrasonic blade, wherein the controller is configured to: measure a first ultrasonic frequency of the ultrasonic blade; measure a second ultrasonic frequency of the ultrasonic blade after measuring the first ultrasonic frequency; calculate a frequency parameter change between the measured first and second ultrasonic frequencies of the ultrasonic blade; correlate the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade based on the plurality of predetermined data correlations to thereby determine the temperature of the ultrasonic blade; and adjust at least one power parameter of the ultrasonic energy to limit the blade temperature to an upper temperature limit. measure a first ultrasonic frequency of the ultrasonic blade; measure a second ultrasonic frequency of the ultrasonic blade after measuring the first ultrasonic frequency; calculate a frequency parameter change between the measured first and second ultrasonic frequencies of the ultrasonic blade; correlate the frequency parameter change of the ultrasonic blade to the temperature of the ultrasonic blade based on the plurality of predetermined data correlations to thereby determine the temperature of the ultrasonic blade; and adjust at least one power parameter of the ultrasonic energy to limit the blade temperature to an upper temperature limit.