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About This Calculator
The dew point is the temperature at which air becomes fully saturated and water vapor begins condensing into liquid. A higher dew point means more moisture in the air and greater discomfort, regardless of the actual temperature. This tool computes dew point from temperature and humidity to help assess comfort levels and fog potential.
Quick Tips
- 1 A dew point above 65°F feels oppressively humid for most people.
- 2 Subtract dew point from temperature and multiply by 400 to estimate cloud base.
- 3 Dew point is more reliable than relative humidity for gauging comfort.
Example Calculation
Temperature 78F, relative humidity 55%.
Dew point: 61F (16.1C) | Comfort: comfortable to slightly humid | Fog unlikely
What Is the Dew Point?
The dew point is the temperature at which air becomes saturated and water vapor begins to condense into liquid water (dew). A higher dew point means more moisture in the air. The dew point can never exceed the air temperature.
Dew Point and Comfort
Dew points below 55°F feel comfortable and dry. Between 55°F and 65°F feels pleasant. Between 65°F and 70°F feels humid and sticky. Above 70°F feels oppressive and tropical. Above 75°F is extremely uncomfortable and rarely occurs outside tropical regions.
How Dew Point Is Calculated
The Magnus formula approximates dew point from temperature and relative humidity. First, calculate a gamma value using the natural logarithm of humidity and temperature constants, then apply the inverse formula to get the dew point temperature.
Dew Point vs Relative Humidity
Dew point is a better measure of moisture than relative humidity. Relative humidity depends on air temperature (it changes throughout the day), while dew point directly indicates the amount of moisture in the air. A dew point of 65°F always feels the same.
Frequently Asked Questions
Most people find dew points below 60°F comfortable. Between 60°F and 65°F is noticeable but not unpleasant. Above 65°F feels humid and sticky. Above 70°F is very uncomfortable, and above 75°F is oppressive and potentially dangerous.
Relative humidity changes with temperature even if moisture levels stay the same. A 50% humidity at 90°F has much more moisture than 50% humidity at 50°F. Dew point directly measures moisture content, providing a consistent comfort indicator.
At night, surfaces cool by radiating heat. When the surface temperature drops to the dew point, moisture in the air condenses on those surfaces as dew. Clear, calm nights produce the most dew because surfaces cool more efficiently.
No. The dew point can equal the air temperature (at 100% relative humidity) but never exceed it. When the temperature drops to the dew point, fog or dew forms. The maximum dew point equals the current air temperature.