The invention relates to a method and a system for detecting the risk of icing on aerodynamic surfaces lapped by a fluid flow (F), in particular on load-bearing surfaces of fluid machines, of the type comprising a temperature sensor (20). The system is characterized in that the temperature sensor (20) is located close to the aerodynamic surface (5S) to be monitored for detecting the temperature of the surface (5S), and that the system comprises a rain sensor (30) located close to the surface (5S) for detecting the presence of water on said surface (5S). The system can thus detect the risk of icing on aerodynamic surfaces in a very effective, simple and inexpensive manner.