In this case, this window of the world is not covered by rain. In fact, since it is in Arizona, it has likely seen very little rain. To some extent, you can tell the age of the window by the arrangement and size of the panes of glass. The older the window, the smaller the panes and the muntins, grilles, grid or windowpane dividers. All of the terms are used for the parts of the window dividing up the glass.