What Is the Dew Point?
The dew point is the temperature at which air must be cooled, at constant pressure, for water vapor to condense into liquid water. When the air temperature drops to the dew point, the air becomes fully saturated and moisture begins to form on surfaces as dew, fog, or frost.
Unlike relative humidity, which changes as temperature rises and falls throughout the day, the dew point stays relatively constant. This makes it a more reliable indicator of how much moisture is actually in the air and how uncomfortable it will feel outside.
A dew point below 50°F (10°C) feels dry and crisp. Above 65°F (18°C) it starts to feel muggy. Above 70°F (21°C) it feels oppressive – the kind of humidity that makes a hot day feel genuinely dangerous.
Dew Point vs. Relative Humidity
Relative humidity and dew point both measure moisture in the air, but they tell you different things.
Relative humidity is a percentage that describes how close the air is to being fully saturated at the current temperature. The problem is that relative humidity changes constantly as temperature rises and falls. On a hot afternoon, relative humidity drops even if the actual moisture content of the air hasn’t changed at all.
Dew point is an absolute measure. It tells you the actual moisture content of the air regardless of temperature. This is why meteorologists prefer dew point over relative humidity when assessing comfort. A dew point of 65°F feels just as sticky whether the air temperature is 75°F or 95°F.
As a general rule: if you want to know how humid it feels, check the dew point. If you want to know how close it is to raining or fogging, check relative humidity.
What Is a Comfortable Dew Point?
Here’s a quick guide to dew point comfort levels:
Below 50°F (10°C) — Dry: The air feels crisp and dry. Common in winter and arid climates. Very low dew points can cause dry skin and static electricity.
50–60°F (10–16°C) — Comfortable: The ideal range for most people. The air feels pleasant with no stickiness.
60–65°F (16–18°C) — Noticeable: Humidity becomes apparent but not uncomfortable for most people.
65–70°F (18–21°C) — Humid: Sweating becomes less effective at cooling the body. Outdoor activity feels more tiring.
70–75°F (21–24°C) — Very Humid: The air feels heavy and sticky. Prolonged outdoor exertion is not recommended.
Above 75°F (24°C) — Oppressive: Dangerous humidity levels. Heat-related illness risk is elevated. These conditions are rare in most climates but occur regularly in the tropics and Gulf Coast states during summer.
Dew Point and Frost Risk
When the dew point is at or below 32°F (0°C), frost can form on exposed surfaces when air temperature drops to that level overnight. This is particularly important for gardeners and farmers: a dew point near freezing combined with clear skies and calm winds overnight is a strong indicator of frost risk.
Clear nights allow heat to radiate away from the ground rapidly. When the surface temperature drops to the dew point, moisture freezes on contact with plants, cars, and other surfaces. Even if the official air temperature forecast stays above freezing, surface frost is possible if conditions are right.
Use our Frost Risk Calculator for a more detailed frost assessment based on your overnight conditions.
Dew Point for Pilots and Aviation
Dew point is critical in aviation. When air temperature and dew point are close together (within 4°F / 2°C) fog or low clouds are likely to form. Pilots check the temperature-dew point spread before every flight as part of standard weather briefing.
A small spread means the air is nearly saturated and visibility could drop rapidly. A large spread means clear, dry conditions are likely to persist.
How to Monitor Dew Point at Home
Any home weather station that measures temperature and relative humidity can calculate dew point automatically. Most modern stations display dew point alongside temperature and humidity on their console and app.
Our top pick for monitoring dew point at home is the Ambient Weather WS-2902C. It measures temperature, humidity, and dew point and displays all three in real time on its console and mobile app.
Reviewed by Ed Oswald
Lead Reviewer, Weather Station Advisor
Ed has covered consumer technology and weather instruments for Digital Trends, PC World, and the New York Times for over 20 years. He has personally tested every station recommended on this page.