When searching Google for a term like "weather" or "temperature" it helpfully provides a widget with your location's weather information. In the wind tab, I always assumed that the size of the arrows was proportional to the wind speed, until today. The arrows for 15 and 16 are drastically different, despite being 1mph difference, while the arrows for 9 and 15 are extremely close to being the same size, despite the 6mph difference.
I've tried searching for an explanation, but couldn't find anything. What exactly does the arrow size mean?