露点計算ツール
The detailed guide below is currently available in English.
What the dew point tells you
The dew point is the temperature at which air becomes saturated — cool it that far and water vapor starts condensing into dew, fog, or sweat-soaked discomfort. Unlike relative humidity, which swings with temperature, the dew point is a direct measure of how much moisture the air actually holds, which is why meteorologists trust it to describe mugginess.
Choosing a comfort band
Below 10°C (50°F) the air feels dry; 10–15.5°C (50–60°F) is the comfortable middle ground most people enjoy. From about 16–21°C (61–70°F) the air feels distinctly humid, and above 21°C (70°F) it turns oppressive — even a fit person walking outside will feel it. Home dehumidifiers usually aim for an indoor dew point near 12°C (mid-50s °F).
よくある質問
Why use dew point instead of relative humidity?
Relative humidity depends on the temperature: the same air reads 50% at noon and 90% after dark. The dew point moves only when real moisture is added or removed, so it compares fairly across the day.
What does a dew point above the air temperature mean?
It cannot happen. Saturation caps the dew point at the current temperature, which is the 100% humidity case — the temperature, dew point, and wet-bulb readings all meet.
How is this different from the heat index?
The heat index estimates heat stress on the body from temperature plus humidity, while the dew point is a physical property of the air itself. High dew points are exactly what drive the heat index upward.