Fire emissions injected into the atmosphere are crucial input for air quality models. This information is available globally using fire radiative power (FRP) observations, converted into smoke constituents. In case of a missing observation after ignition, a practical choice is to assume persistence. As an improvement we propose the use of the Canadian Fire Weather Index (FWI) to predict the FRP evolution. We show that the FWI is able to capture weather-related changes in fire activity well.