If the temperature-dewpoint spread is small and decreasing, and the temperature is 62 degrees F, what type of weather is most likely to develop?

• A. Fog or low clouds
• B. Clear skies
• C. Thunderstorms
• D. Windy and hot

Answer: (A)

When the temperature-dewpoint spread is small and decreasing, the air is becoming nearly saturated and condensation is likely to occur. Condensation forms water droplets, which show up as fog near the surface or as low clouds aloft. At about 62°F, if the dewpoint is close to that temperature and the spread is shrinking, you’re tipping into conditions where fog or low stratus clouds are most likely to develop, especially with light winds and nighttime cooling.

Clear skies happen when the air is not near saturation, which would mean a larger spread between temperature and dewpoint. Thunderstorms require atmospheric instability and lifting mechanisms, not just high moisture. Windy and hot implies warm, dry air with stronger mixing, not the near-saturation scenario described.