The invention relates to a system (102) for measuring a velocity of a fluid (104) flowing through a flow channel (106). The system comprises a heating element (108) configured for generating a thermal marker in the fluid (104) in response to a predetermined time-varying level of power provided to the heating element (108). The system (102) furthermore comprises a sensor arrangement (110) for generating a measurement signal (112) indicative for the velocity of the fluid (104) flowing through the channel (106). Herein, the sensor arrangement (110) is configured for measuring a time series of the primary temperature (114) of the fluid (104) at a predetermined primary location. The primary location and the heating element (108) are situated on an axis having at least a component parallel to the longitudinal axis (119) of the flow channel (106). The measurement signal (112) is based on the maximum value (120) of the time series of time series of the primary temperature (114) in response to the thermal marker.