A dual readout temperature difference integrator for integrating temperatures in the range of 0° to 50°C with time is described. Temperature differences are integrated whenever the sensed temperature exceeds the threshold temperature for the particular readout. The two thresholds are independently selectable in one degree steps from 0° to 49°C. Additional threshold selects and readouts could be added as required. The integrator's digital readouts are in units of °C-day and have an accuracy within ±1.1% of the indicated values. A digital display of the measured temperature, with a resolution of 0.1°C, is also provided. The display is updated once per second.