One of the most common questions I get as a meteorologist is: "Why does it feel so humid today?" While many people instinctively check the humidity percentage on their phone or weather dashboard, there’s another, often more telling number you should pay attention to: the dew point.

What is Dew Point?

Simply put, the dew point is the temperature at which air becomes fully saturated with water vapor, and water begins to condense into dew. If you cooled the air down to the dew point, you would see dew form on grass or surfaces. But in meteorology, dew point is more than a measure of when you’ll see drops on your morning lawn—it’s a direct indicator of how much moisture is in the air.

Dew Point vs. Relative Humidity

While relative humidity (%RH) compares the current water vapor in the air to the maximum amount air can hold at a given temperature, it’s a moving target: warm air can hold more moisture than cold air. Dew point, on the other hand, is an absolute value—no matter what the air temperature is, the dew point tells us the actual amount of moisture present.

Here’s a rule of thumb: the higher the dew point, the more moisture there is in the air. If the dew point climbs into the 60s °F (15–20°C), you’ll start to feel sticky and uncomfortable. Dew points in the 70s °F (over 21°C) feel downright tropical!

Why Dew Point Matters

• Comfort: High dew points mean your sweat doesn’t evaporate easily, making it feel muggy and harder to cool off.
• Forecasting: Meteorologists watch rising dew points as a signal for potential thunderstorms. High moisture at the surface provides fuel for storm development.
• Agriculture & Health: Dew point affects soil moisture, risk of frost, and even the likelihood of heat-related illnesses, influencing everything from farming to sports.

How to Use Dew Point in Your Daily Life

Instead of checking the relative humidity, try glancing at the dew point:

• Below 50°F (10°C): Dry and comfortable
• 50–59°F (10–15°C): Slightly humid
• 60–69°F (15–20°C): Getting muggy
• 70°F+ (21°C+): Oppressive humidity

So next time the air feels heavy, look at the dew point—it just might reveal the true reason behind the stickiness in the air. Happy weather-watching!

— Rabir