Live vehicle probe data is obtained relating to the movement of vehicles with respect to time along a navigable element. The probe data is used to determine a current speed of travel along the navigable element, which is compared to the free flow speed of travel for the navigable element. When the current speed of travel along the element is reduced relative to the free flow speed for the navigable element by less than a threshold associated with identifying a congestion event, and obtained weather data indicates the navigable element is affected by one or more adverse weather conditions, then a weather event is generated. If the reduction in speed of travel is of a size sufficient to trigger the generation of a congestion event, and obtained weather data again indicates the navigable element is affected by one or more adverse weather conditions, then one or more attributes of the congestion event can be used to determine if the cause of the congestion can be attributed to the adverse weather.