Incidentally, manhole and sewer covers seem to be one of the few good things in our culture. The pattern may wear off, but they never seem to wear out. I suppose that one of these days they'll start making them out of plastic. As to the weather, dew point and humidity are related. Dew point is the temperature at which dew forms.
Humidity is the amount of water that the air contains.
The more moisture in the air, the easier dew forms. I have always been amazed at the people who produce our wonderful music. It must be like searching for gold. It's out there, but finding it is another matter. He said that he was sitting on the sofa watching TV and let a lot of them float by that Bob Dylan caught.