Dew Point Calculator
Dew Point Comfort Scale
About Dew Point
Dew point is the temperature at which air becomes saturated with water vapor and condensation begins to form. It's a better indicator of comfort than relative humidity because it doesn't change with temperature.
Related Calculators
Understanding Dew Point
What is Dew Point?
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When this point is reached, water vapor in the air begins to condense into liquid water (dew). The dew point is always less than or equal to the air temperature.
Why Dew Point Matters
Dew point is the best measure of how comfortable the air feels. Unlike relative humidity, which changes with temperature, dew point stays constant throughout the day. A high dew point means lots of moisture in the air, making it feel muggy regardless of temperature.
Dew Point vs. Relative Humidity
Relative Humidity
- Percentage of maximum moisture air can hold
- Changes with temperature
- Can be misleading (50% RH at 90°F feels muggy)
- Depends on both moisture AND temperature
Dew Point
- Absolute measure of moisture in air
- Does not change with temperature
- Directly indicates comfort level
- Depends only on moisture content
Comfort Levels by Dew Point
| Dew Point (°F) | Comfort Level | Description |
|---|---|---|
| < 50°F | Dry | Very comfortable, pleasant |
| 50-55°F | Comfortable | Ideal conditions |
| 55-60°F | Pleasant | Slightly noticeable humidity |
| 60-65°F | Sticky | Becoming uncomfortable |
| 65-70°F | Humid | Uncomfortable for most people |
| 70-75°F | Oppressive | Very uncomfortable |
| > 75°F | Miserable | Dangerous, extreme discomfort |
Practical Applications
Home Comfort
- Ideal indoor dew point: 45-55°F
- Use dehumidifier if above 60°F
- Prevents mold and mildew growth
- Protects furniture and instruments
Weather Forecasting
- Predicts overnight fog formation
- When temp drops to dew point = dew/fog
- Higher dew point = more likely rain
- Helps predict thunderstorm intensity
Key Facts
- Dew point can never exceed the air temperature
- When dew point equals air temp, relative humidity is 100%
- Cold air holds less moisture, so winter dew points are lower
- Tropical regions often have dew points above 70°F
- Desert dew points can be below 0°F
Frequently Asked Questions
What is dew point and why does it matter?
Dew point is the temperature at which air becomes saturated and water vapor condenses into dew. Unlike relative humidity, dew point directly indicates comfort level - above 65°F feels humid, above 70°F feels oppressive. It's the best measure of how 'muggy' the air feels.
What is a comfortable dew point?
A dew point below 55°F feels comfortable and dry. Between 55-65°F is noticeable but tolerable. Above 65°F feels humid and sticky, while above 70°F is considered oppressive. Indoor comfort is best maintained at dew points between 45-55°F.
Why is dew point better than relative humidity for measuring comfort?
Relative humidity changes with temperature (50% at 90°F feels muggy, but 50% at 60°F feels dry). Dew point measures absolute moisture in the air and stays constant regardless of temperature, making it a more reliable comfort indicator.
How do I calculate dew point from temperature and humidity?
Enter the current air temperature and relative humidity in the calculator above. It uses the Magnus formula to calculate the dew point temperature. When the air temperature drops to the dew point, condensation (dew, fog, or frost) will form.