Why Does 85 Degrees Feel So Much Better Today? It’s All About the Dewpoint

Walk outside across much of the Piedmont and western North Carolina this afternoon and you may notice something almost immediately: it feels good.

Temperatures across much of the region will still reach the lower to mid-80s. That's certainly not cool, and it's still August in North Carolina. But compared with some of the hot, sticky weather we've experienced recently, today's temperatures will feel considerably more comfortable.

From Rowan, Davie and Davidson counties through the Charlotte Metro, Triad and foothills, a drier air mass is spreading into the region behind a cold front.

So how can temperatures in the 80s feel completely different from one day to another?

The answer has a lot to do with something I frequently mention in the forecast: the dewpoint.

What Is the Dewpoint?

The dewpoint is one of the best measurements meteorologists have for determining how much moisture is actually present in the atmosphere.

Technically, the dewpoint is the temperature to which air would need to cool for the air to become saturated. But you don't need to remember the technical definition to understand why it matters.

Here's the simple version:

The higher the dewpoint, the more moisture there is in the air — and the muggier it tends to feel.

That's why I pay close attention to dewpoints when talking about how comfortable — or uncomfortable — a summer day will feel.

Relative humidity is useful, but it can change considerably as the temperature changes throughout the day. Dewpoint gives us a better indication of the actual amount of moisture present in the air.

A Simple Dewpoint Guide

There isn't one exact dewpoint at which everyone suddenly becomes uncomfortable. People experience humidity differently.

But as a general summertime guideline:

• 55° or lower: Dry and very comfortable
• 55° to 60°: Comfortable
• 60° to 65°: Some moisture is noticeable, but generally still pleasant
• 65° to 70°: Increasingly humid
• 70° and higher: Muggy and uncomfortable
• Mid-70s and higher: Oppressively humid for many people

Anyone who has spent a summer in North Carolina knows what those 70-plus-degree dewpoints feel like.

You walk outside and immediately notice the heavy, sticky air.

Today's air mass is very different.

What's Different Across the Region Today?

A cold front has moved through much of the region, and behind it is a noticeably drier air mass.

Northwest flow behind the front is helping transport that drier air into the Piedmont and surrounding areas. Dewpoints across parts of the region are dropping into the 50s and lower 60s.

That is a significant change from the tropical-feeling humidity we frequently experience during August.

Afternoon temperatures will still be warm. Many locations from the Charlotte area through Rowan County, the Triad and surrounding Piedmont will reach the lower to mid-80s.

But with substantially less moisture in the atmosphere, those temperatures will feel much more comfortable.

Same August sunshine. Much different air mass.

And you're probably going to notice the difference as soon as you step outside.

Why Humidity Makes Heat Feel Worse

Your body has its own natural cooling system: sweat.

When you're hot, your body produces perspiration. As that moisture evaporates from your skin, it removes heat and helps cool your body.

When the atmosphere already contains a lot of moisture, evaporation becomes less efficient. Sweat doesn't evaporate as readily, so your body's natural cooling process doesn't work as effectively.

That's one reason a humid North Carolina afternoon can feel considerably hotter than the actual temperature.

When the air is drier, perspiration can evaporate more efficiently, allowing your body to cool more effectively.

So even if today's temperature isn't dramatically lower than some other summer days, your body notices the difference in moisture.

85 Degrees Isn't Always the Same 85 Degrees

Imagine two North Carolina summer afternoons.

Day One:
Temperature: 85°
Dewpoint: 73°

Day Two:
Temperature: 85°
Dewpoint: 57°

The thermometer reads exactly the same temperature.

But those two afternoons won't feel remotely the same.

The first would feel sticky and humid. You might walk outside and immediately wonder how quickly you can get back into the air conditioning.

The second could feel surprisingly pleasant, particularly with a breeze and some shade.

That's why temperature alone doesn't tell the entire story.

It's also why you'll sometimes hear people say, "It doesn't feel like 85 degrees today."

They're noticing the difference in atmospheric moisture even if they don't realize it.

But My Weather App Says the Humidity Is High This Morning

Here's where things can get confusing.

You might wake up on a comfortable morning, check your weather app and see relative humidity of 80%, 90% or even close to 100%.

How can the air eventually become comfortable if the humidity is supposedly that high?

Because relative humidity is relative to temperature.

Relative humidity tells us how close the air is to saturation at its current temperature.

During the early morning, temperatures are usually near their daily minimum. Cooler air reaches saturation more easily, so relative humidity commonly becomes very high around sunrise.

As temperatures climb during the afternoon, relative humidity can fall dramatically.

That's why looking only at relative humidity can sometimes give you the wrong impression about how muggy the afternoon will actually feel.

Dewpoint is usually the number I prefer when determining how comfortable the air mass will feel.

The Difference Is Being Felt Across the Piedmont

This isn't just a Rowan County weather story.

The drier air is spreading across a large portion of the region.

Communities across the Charlotte Metro, southern Piedmont, northern Piedmont, Triad and foothills will experience the change.

For Rowan County, temperatures today will reach around the mid-80s.

Davie and Davidson counties are also looking at highs in the mid-80s.

Similar temperatures are expected across much of the surrounding Piedmont.

What makes Sunday stand out isn't necessarily the temperature.

It's how those temperatures feel.

For late August, this is a pretty nice air mass.

Why Tonight Will Feel So Nice

The lower humidity also helps explain another noticeable part of the forecast: cooler nighttime temperatures.

Many locations across the Piedmont will fall into the upper 50s and lower 60s tonight.

Rowan County is forecast to fall to around 61 degrees.

Davie County could reach around 60 degrees.

Davidson County could fall to around 59 degrees.

Those are some very comfortable numbers for an August night in North Carolina.

Clear skies, light winds and a relatively dry air mass will allow temperatures to fall efficiently after sunset.

For some locations, opening the windows tonight might actually sound pretty appealing.

Is This an Early Taste of Fall?

It might feel a little like fall, especially early Monday morning.

But don't put away the summer clothes just yet.

This isn't the beginning of a permanent seasonal change.

We're still in August, and summer warmth and humidity can easily return across North Carolina well into September.

What we're experiencing is a temporary push of cooler and, more importantly, drier air behind a cold front.

Cold fronts don't always bring dramatic temperature drops. Sometimes their biggest impact during the summer is replacing a very humid air mass with a much drier one.

That's exactly what we're experiencing this weekend.

How Long Does the Comfortable Weather Last?

The good news is that this isn't just a one-day break.

Much of the Piedmont should enjoy comfortable humidity through Monday and Tuesday, with plenty of sunshine and temperatures generally remaining in the 80s.

By Wednesday, however, the atmosphere begins changing again.

Moisture will gradually return from the south and east, allowing humidity to increase.

Then Thursday brings a better opportunity for showers and thunderstorms across the region as another weather system approaches.

The more humid and unsettled pattern could continue into the end of the week and next weekend.

So if you're a fan of lower humidity, Sunday through Tuesday is your window.

Weather 101 with Rowan County Weather

Today's weather across the region provides a perfect example of why I don't look at temperature alone when describing how a day will feel.

Temperature tells us how warm the air is.

Dewpoint tells us something equally important:

How much moisture is in that air?

Put those two pieces together and you get a much better idea of what conditions will actually feel like when you walk outside.

So the next time the forecast calls for 85 degrees, don't automatically assume it's going to feel hot and sticky.

Check the dewpoint.

An 85-degree afternoon with a dewpoint in the 70s can feel miserable.

An 85-degree afternoon with a dewpoint in the 50s?

That's a completely different kind of North Carolina summer day.

And today, much of our region gets to enjoy the better version.

— Rowan County Weather