Which is colder, dry cold or humid, damp cold? Does it matter?

Shirley P. Olin

Orlando – The memes are everywhere.

Images of a person sitting on a beach in a winter coat, boots, and coffee with the caption: “Floridians be like it’s 70 degrees time to get out the winter clothes.” Come on, we don’t have coats! I’m kidding. We do. Sometimes. Even friends and relatives may make comments like: “50 degrees isn’t cold, 9 degrees is cold. Florida isn’t that cold in winter.”

IT’S STILL COLD OUT 🥶 | It was yet another chilly start Wednesday across Central Florida, with low temperatures ranging from the mid-30s north of Orlando to the 40s and 50s elsewhere. https://bit.ly/3tC3yhr

Posted by News 6 WKMG / ClickOrlando on Wednesday, January 19, 2022

We won’t dispute the fact that winter elsewhere is colder than the typical Florida winter. It is after all, why many people vacation here during the frigid winter months. Despite popular belief and a plethora of memes, it still gets downright nippy in the Sunshine State. This past weekend was a prime example.

Monday Jan 24th many central Florida cities woke up to the 20s! (WKMG)

Lows crashed to the 20s and 30s and we even had frost. That’s cold.

Not to mention there’s another blast of cold air headed to Central Florida this weekend.

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There’s a reason why 50 degrees might not feel cold to those who live in colder climates but does to Floridians. Yes, our bodies are acclimated differently, but there’s more to just being used to the colder winters. It has a lot to do with the wind and although up for debate, the moisture in the air has something to do with it too. The best indicator for how it feels outside is the dewpoint value. Let’s take a closer look at our bodies first before diving into the weather elements.

Understanding Our Body

The human body has an internal thermostat. The hypothalamus, while it performs many functions, the most significant one is maintaining internal homeostasis.

Image of a brain. (Image provided by Henry Ford Health System.)

Keeping our body temperature balanced while in different environments falls under that category. When it’s cold some may end up shivering. That’s the body’s response to keep warm in a cold environment. In the summer sweat is produced to cool the body to regulate core temperature.

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Why Dewpoint Values Matter

In the summer the warmer air holds more moisture. When highs reach the 90s with dewpoints in the 70s, the air feels hotter than actual temperatures. It’s humid. Meteorologists often urge the public to stay hydrated and to take breaks in the shade to avoid overheating or heat-related illness. When the body produces sweat to cool the body, the more humid the air is, the less the sweat evaporates. It’s the evaporation of the sweat on the skin that cools the body. If it’s a dry heat the sweat evaporates a lot faster and results in maintaining a balanced temperature.

The dewpoint temperature is the measure of the absolute amount of moisture in the air. It represents the value at which a parcel of air needs to be cooled to reach total saturation given the water vapor in the air. For example, if the temperature outside is 70 degrees with a dewpoint value of 70, then the relative humidity is 100%. It’s also referred to as “air you can wear” because you can feel the stickiness in the air outside. The same thing goes if the temperature is 50 and the dewpoint value is 50 the relative humidity is still 100%, but it doesn’t feel as gross as 70 degrees would, right? That’s why dewpoint values are used instead of judging how it will feel based on relative humidity. If that same temperature of 70 degrees had a dewpoint value of 50, then it would feel more comfortable or cooler to someone outside versus walking outside and being greeted by the humid air.

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During winter, cooler air holds less moisture, resulting in lower dewpoint values. Behind a cold front, cooler and drier air often follows. When dewpoint values are low the air feels crisp in the cooler air. That’s not always the case in Florida winters. This is part of living in a tropical environment where typical dewpoints during winter are in the 40s and 50s and our friends to the north have dewpoint values a lot lower near 10-20.

Typical dewpoint values in January for Florida range in the 40s and 50s for central Florida. (NOAA)

When its chilly outside and it rains that’s a good sign there’s a lot of moisture in the air. It’s dropping on the ground it’s so apparent. This is not a dry cold situation, but a humid cold one. Even if it’s not raining, if the air has a lot of moisture in it, then it will feel a bit colder than it really is. Laws of Thermodynamics show that damp air transfers heat more quickly than dry air. As a result, more heat escapes the body making someone feel colder.

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Our clothing choice is a factor too. Think about this. There are super tiny molecules of water in the air that aren’t visible to the naked eye. In humid air, it’s more noticeable than dry air because humid air has a higher moisture content. If someone chooses a long sleeve cotton shirt they will feel colder because the fabric absorbs the moisture lingering in the air more than wool, fleece, or synthetic materials that actually repel moisture. If the air is 50 degrees but with a dewpoint in the 20s or 30s that same cotton material won’t have as much moisture in the air to absorb so the body would feel warmer.

Wait. There’s more.

Wind plays a factor too. In winter there’s the wind chill index.

The science of wind chill. (NOAA)

When the wind is blowing in the cold weather it feels colder because the wind is carrying the heat generated to stay warm away from the body.

This chart shows temperatures and how wind can make it feel colder during winter months. (NOAA)

All these factors make a difference and the dry cold versus humid cold debate continues. The end result: cold is cold. How each person feels in that cold is based on what they’re used to. Think about it. If it’s 46 degrees in Orlando when it’s typically 72 this time of year, people that reside here will be cold. If someone visiting Orlando says it’s not cold, think about the environment they just came from. If they are visiting from a state where the high is barely in the single digits, then yes 40-degree weather won’t feel as cold to that person.

Copyright 2022 by WKMG ClickOrlando – All rights reserved.

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