Dew point is the temperature at which air becomes saturated and water vapour condenses into liquid. When the air temperature drops to the dew point, you get dew, fog, or cloud. A higher dew point means more moisture in the air. Dew point is a better measure of humidity than relative humidity for outdoor comfort.

Why does dew point matter for camping?

Dew point determines tent condensation, fog risk, and personal comfort. When the overnight temperature drops close to the dew point, heavy condensation forms inside your tent and on your gear. In the UK, dew points of 8-14°C are common, meaning condensation is almost guaranteed on cool nights.

What causes morning fog?

Fog forms when air temperature drops to within 2-3°C of the dew point. Radiation fog occurs on clear, calm nights when the ground cools rapidly and chills the air above it. Valley fog forms when cold air pools in low ground. Knowing the dew point helps predict whether fog will form overnight.

How do I measure dew point in the field?

Without instruments, observe: if condensation forms on the outside of a water bottle, the bottle surface is at or below the dew point. Heavy evening dew on grass means the dew point is close to the current temperature. If morning dew is absent, the air is dry and the dew point is much lower than the overnight minimum.

CampCalcs

Dew Point Calculator

Calculate the dew point temperature from air temperature and relative humidity.

Air Temperature

Temperature for this process

Relative Humidity

Enter the relative humidity

How We Calculate This

Magnus Formula

alpha = (17.27 x T) / (237.7 + T) + ln(RH / 100)

Dew point = (237.7 x alpha) / (17.27 - alpha)

Where T = temperature (°C) and RH = relative humidity (%).

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify conditions and use proper safety equipment outdoors.