This particular wind speed indicator hasn’t been functional in ages, but at some point it was probably useful in determining whether or not to go outside for telescope observations. Wind is of concern in astronomy, as it can produce poor seeing and – when really strong – cause telescopes to shake. But wind chill is the more immediate concern. Cold nights can be good for observing, with clear skies and good seeing, but rough on fingers and toes.
All of that standing still, lack of warming sunshine, etc. doesn’t do a lot to counter a cold night. Maybe think ahead and bring along a hot beverage?
An awful lot of that chart is devoted to conditions when no one should be outside at all. One line of thought considers that a chart with all of your category indicators bunched up on the left isn’t the ideal for communicating information visually. Another notes that an endless tundra of negative numbers tells you enough without needing the particulars.
