A method of determining whether one or more navigable elements of a navigable network within a geographic area are still affected by a precipitation weather event, the navigable elements being represented by one or more segments of an electronic map, wherein at least some of the segments of the electronic map are each associated with data indicative of a quantity parameter for the segment, the quantity parameter being indicative of the amount of precipitation remaining on the navigable element or portion thereof represented by the segment, wherein the value of the quantity parameter varies according to a predefined function with respect to time such that the quantity parameter decreases in the absence of any precipitation weather event, and wherein the predefined function is based on temperature data indicative of a current temperature at a location of the navigable element, said method comprising: obtaining weather data indicative of one or more precipitation weather events in the geographic area, wherein each precipitation weather event affects at least a portion of the geographic area; obtaining positional data relating to the movement of a plurality of devices along one or more of the navigable elements with respect to time, and using the positional data to determine a speed of travel of devices along the one or more navigable elements; identifying one or more segments representative of navigable elements within the portions of the geographic area affected by the one or more precipitation weather events, and increasing, for each of the one or more identified segments, the value of the quantity parameter associated with the segment; comparing, for each of the one or more identified segments, the determined speed of travel to an expected speed of travel for the segment, and decreasing the value of the quantity parameter associated with the segment based on the comparison; and generating, for each of the one or more identified segments, data indicative of whether the navigable element or portion thereof represented by the segment is still affected by the one or more precipitation weather events based on the value of the quantity parameter. obtaining weather data indicative of one or more precipitation weather events in the geographic area, wherein each precipitation weather event affects at least a portion of the geographic area; obtaining positional data relating to the movement of a plurality of devices along one or more of the navigable elements with respect to time, and using the positional data to determine a speed of travel of devices along the one or more navigable elements; identifying one or more segments representative of navigable elements within the portions of the geographic area affected by the one or more precipitation weather events, and increasing, for each of the one or more identified segments, the value of the quantity parameter associated with the segment; comparing, for each of the one or more identified segments, the determined speed of travel to an expected speed of travel for the segment, and decreasing the value of the quantity parameter associated with the segment based on the comparison; and generating, for each of the one or more identified segments, data indicative of whether the navigable element or portion thereof represented by the segment is still affected by the one or more precipitation weather events based on the value of the quantity parameter.