Calculate dew point spread and estimate fog risk using temperature, dew point, and wind conditions. This free aviation calculator helps pilots improve weather awareness during preflight planning.
Enter air temperature and dew point using the same unit, then select a wind condition to estimate relative fog risk.
This tool estimates relative fog risk only and should be used alongside actual weather data and trend awareness.
Dew point spread is the difference between air temperature and dew point. When the spread becomes very small, the air is close to saturation and fog becomes more likely if other conditions support it.
Pilots often watch dew point spread during cool, moist, and calm conditions because nighttime cooling can reduce the spread further and allow fog to form.
No. A small spread increases fog potential, but actual fog formation also depends on wind, terrain, sky cover, recent weather, moisture availability, and temperature trends.
Calm or light wind can help surface air cool and saturate more easily, which may support radiation fog formation in the right conditions.
Yes. The calculator works with either unit as long as both the temperature and dew point use the same unit.
No. This calculator is a weather-awareness aid. Always use official observations, TAFs, METARs, forecast discussions, and current weather information for real planning decisions.