Dew Point
The dew point is the temperature to which air must be cooled to become saturated, so that water vapor begins to condense into dew or fog. The higher the dew point, the more moisture is in the air. In summer, a dew point of 55°F or lower feels dry and comfortable, and 65°F or higher feels muggy.
Why It Matters
Dew point is the most direct everyday measure of how humid the air feels, because it tracks the actual amount of water vapor. Relative humidity also depends on temperature, which makes it misleading on its own. A 30°F morning with a 30°F dew point has 100% relative humidity, while an 80°F afternoon with a 60°F dew point has only 50%, and the afternoon is the one that feels humid.
When the air temperature falls to the dew point, the air is saturated, and dew, fog, or frost (when it is below freezing) can form.
How Dew Point Feels in Summer
| Dew point | How it feels |
|---|---|
| 55°F or lower | Dry and comfortable |
| Between 55°F and 65°F | Becoming sticky, with muggy evenings |
| 65°F or higher | Lots of moisture in the air, becoming oppressive |
Frequently Asked Questions
What is a comfortable dew point?
55°F or lower feels dry and comfortable in summer. Between 55°F and 65°F the air starts to feel sticky, and at 65°F or higher it feels muggy and increasingly oppressive.
Is dew point the same as humidity?
No. Dew point is a temperature that reflects how much water vapor is in the air. Relative humidity is a percentage that compares that moisture with the most the air could hold at its current temperature, so it changes through the day even when the moisture does not.
Can the dew point be higher than the temperature?
No. The dew point can equal the air temperature, which means 100% relative humidity, but it does not exceed it.
Related Terms
Relative Humidity
The ratio of the current absolute humidity to the maximum possible humidity at the current temperature, expressed as a percentage. 100% relative humidity means the air is fully saturated. Relative humidity changes with temperature even if moisture content stays the same.
Humidity
The amount of water vapor present in the air. Absolute humidity measures the actual water content, while relative humidity expresses how close the air is to saturation at its current temperature, shown as a percentage.
Heat Index
The heat index is how hot it feels when relative humidity is combined with the air temperature. Humid air slows the evaporation of sweat, so the body cools less efficiently and feels hotter than the thermometer reads. At 100°F with 55% relative humidity, the heat index is 124°F.
Wet-Bulb Temperature
Wet-bulb temperature is the lowest temperature air can reach by evaporating water into it. It is always at or below the air temperature, and the drier the air, the larger the gap between the two. Forecasters use it to judge heat stress and how much falling rain or snow can cool the air.
Freezing Fog
Fog that forms when air temperature is below 32°F (0°C), depositing ice crystals on exposed surfaces. Freezing fog creates treacherous driving conditions and can coat everything with a layer of rime ice.
Frost
Frost is a thin layer of ice crystals that forms on surfaces when they cool to 32°F (0°C) or below and water vapor in the air freezes onto them. It is the surface that has to reach freezing, not the air: frost can form while the official air temperature is still in the mid 30s.
Dew Point: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
In-depth guide
Dewpoint Explained: The Most Important Weather Number You're Ignoring
Learn what dewpoint really means, why it matters more than humidity for comfort, and how to use it for fog prediction, outdoor planning, and understanding mugginess.
Weather Education
Frost Advisory vs Freeze Warning vs Hard Freeze: What Each One Means
A Frost Advisory usually means lows of 33 to 36°F, a Freeze Warning 32°F or colder, and a hard freeze about 28°F or colder. Learn why frost forms above freezing, why the alerts stop in late fall, and what to protect at each level.
Weather Safety
The Heat Index Explained: How Hot It Really Feels and How to Stay Safe
Learn what the heat index is, how temperature and humidity combine into a 'feels like' temperature, how to read the NWS heat index chart, and how to stay safe in extreme heat.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Tool
Dew Point Calculator
A free tool for working this out with your own numbers.
Guide
Dew Point vs Humidity
Learn why dew point is often the better way to judge comfort and storm moisture.
Tool
Cloud Base Calculator
Estimate cloud base height from temperature and dew point spread.
Tool
Temperature Converter
Convert between Fahrenheit, Celsius, and Kelvin instantly.
Sources
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