(WHTM) — When temperatures rise, sometimes the air can feel dry and comfortable. But, sometimes it can feel downright tropical outside. This is caused by moisture in the air and it makes the air temperature feel much hotter and much more uncomfortable.
But, sometimes you see two different measurements of the moisture in the air. One of them is the dewpoint and the other one is relative humidity.
So, what is the difference, if there really is one?
To find out, let’s dive into what dewpoint is and what relative humidity is.
Dewpoint is a more direct measure of moisture in the air. So as the air cools to the dewpoint temperature, the air becomes saturated, and dew or fog can be formed. This happens at night or in the morning, and this is when the humidity gets close to 100%.
The definition of relative humidity, as defined by the National Weather Service office in Louisville, is expressed as a percent. It also measures water vapor but is relative to the temperature of the air.
In other words, it is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature.
So, dewpoint is more of an accurate representation when it comes to measuring the actual moisture in the air. If the dewpoint and temperature are close to being the same, the relative humidity will be near 100% This is because the air is completely saturated.
One of the main questions the abc27 weather team gets is why they use the dewpoint, rather than the humidity in their forecasts. abc27 meteorologist Dan Tomaso explained that it is just a more accurate measurement of moisture.
“The relative humidity is calculated using temperature, so changes in temperature cause the humidity to rise and fall. As a result of this calculation/relationship, the humidity will always be higher in the morning than the afternoon if it is a sunny day,” Dan said.
“Dewpoint temperatures do not fluctuate as much and are a constant indicator of the moisture in the air throughout the day. We also use dewpoints to predict nighttime temperatures and they give us clues about the chances for storm activity,” he added.
Dewpoint is just a more accurate representation of the moisture in the air, because it doesn’t fluctuate as much, and that is why most meteorologists like to show the dewpoint rather than relative humidity.
For more information about the dewpoint and also how it relates to the dewpoint, click here.