1. A method for generating a personalized run weather index comprising: receiving, by computer-executable instructions of an index calculator executing on a computing device, input data comprising a location; retrieving, by the index calculator, meteorological conditions in accordance with said input data by querying a weather database using said input data to obtain a set of query database results containing a corresponding meteorological value for each of said meteorological conditions; determining, by the index calculator, a contribution value of each retrieved meteorological value, the contribution value of each retrieved meteorological condition indicative of its relative effect on a fitness running condition, the contribution value of each retrieved meteorological condition is determined based on a look-up operation to a table that correlates a plurality of meteorological values of a corresponding meteorological condition to a plurality of contribution values, respectively; receiving, by the index calculator, an adjustment to an impact level of one of the retrieved meteorological conditions so as to adjust a relative effect of the one of the retrieved meteorological conditions on the fitness running condition for a particular user; adjusting, by the index calculator, the plurality of contribution values for the table of the one of the retrieved meteorological conditions based on the adjustment to the impact level; determining, by the index calculator, a personalized run weather index from a combination of the determined contribution values of the retrieved meteorological conditions, said run weather index indicative of an outdoor fitness running condition and having a value between a predetermined minimum and predetermined maximum; and providing, by the index calculator, the run weather index in a format suitable for display in a user interface.