Unless you own anti-fog goggles (and even those can fog up) it doesn't take much body warmth to put you into a fuzzy state of out-of-focus. The combination of heat rising up from your shirt or down from your helmet can create some seriously steamy vision. Add high humidity to the mix, and it can become a challenge just trying to wear one of the most fundamental pieces of safety gear.
The solution is simple: a few drops of Dawn, Joy, or any liquid dishwater soap. Start with clean goggles and make sure you have a large, dry soft lens cloth. Put two drops of soap on the front and back of both lenses and polish clean until dry without water.
Once complete, your goggles will stay fog free for a couple of hours. The coating will also help dust stay off the lenses and make them easier to clean during the day.