A novel anemometer was designed and implemented for the simultaneous measurement of velocity and temperature in air flows with a single hot wire probe. The principle of periodically varying the overheat ratio of the wire was selected and applied through a parameterizable electronic chain. The specific methods developed for the calibration procedure and the signal processing are explained. The accuracy of the measurements has been assessed by means of Monte-Carlo simulations. Some examples of results are given for two types of turbulent non-isothermal flows, a coaxial heated jet and a low speed thermal mixing. The particular interest of the synchronism of the two measurements is emphasized.