Some weathervanes include wind cups, which can give you a rough idea of how strong the wind is. Other than that, weathervanes don’t provide much in the way of weather information, although you can mount a rain gauge and other weather station instruments to them. Unless these instruments are wireless, however, you won’t be able to place them on a roof and receive much information from them.What a weathervane can do by itself is provide you with a rough forecast based on its behavior. For example, if the weathervane shifts from west to east, it may indicate that a storm is headed your way. Similarly, if it suddenly shifts to show wind from the south, it may indicate that warm air is headed your way.