As photographers there are many elements of a photograph that we can control: lighting, composition, depth of field, etc. However, during event photography it is impossible to control the natural elements such as sun, clouds and yes - rain.
However, we should welcome the rain, as it can create powerful mood in images that is almost impossible to create otherwise. During the final cross country meet of the season (for my JV runner anyway) we had a light and persistent rain that provided a unique mood to my photos. The natural elements, when combined with some post processing made for powerful sports photography.