Temperature’s Impact on Wood Moisture Content

If you want to take accurate wood moisture measurements, you need to understand how ambient temperature, relative humidity, and wood moisture content interact.

But that’s not all.

You also need to understand how temperature affects your wood moisture meter, because temperature doesn’t affect pin-type and pinless meters the same way. We’ll talk more about this in a bit. But first, let’s go over some basics about temperature and wood moisture content.

• How Do Temperature and Humidity Affect Wood?
• Relative Humidity and Wood Moisture Content
• How Does Moisture Affect Wood?
• How Temperature Affects Your Wood Moisture Meter

How Do Temperature and Humidity Affect Wood?

First of all, what do we mean when we talk about the moisture content of wood? Let’s quickly go over the answer to that before we continue.

The moisture content (MC) of wood equals the weight of the water in the wood divided by the weight of the oven-dry wood, multiplied by 100 to express it as a percentage. Note that it’s possible for the moisture content to be over 100% if the water present in the wood weighs more than the wood itself.

Now let’s talk about how temperature and humidity affect wood.

Relative humidity has a much greater effect on wood’s moisture content than temperature does. Temperature’s direct effect is small; its bigger influence comes through the way it changes the relative humidity.

If you placed a piece of wood flooring in a room where the temperature rose and fell while the relative humidity stayed constant, its moisture content would change only slightly.

But if the temperature stayed constant while the relative humidity rose and fell, its moisture content would rise and fall with it. You can see this for yourself in an equilibrium moisture content (EMC) table.

So, why does relative humidity have a greater impact on moisture in wood than temperature? Let’s find out.

Relative Humidity and Wood Moisture Content

Wood is a hygroscopic material. That means it’s constantly reacting to changes in its environment by absorbing and releasing moisture.

If the wood’s MC is lower than the EMC for the surrounding temperature and humidity, the wood absorbs moisture from the air until it reaches that EMC. The reverse is also true.

In a dry environment, wood releases moisture until it reaches balance. That balance point, where the wood is neither gaining nor losing moisture, is the EMC.

So it’s mainly the relative humidity, not the temperature, that changes the moisture content of wood.

Prior to putting down hardwood flooring, building a cabinet, or any other project, wood needs time to adjust to the environment where it will be used. In other words, it needs time to reach EMC. Skipping this step can cause moisture-related problems later, because wood shrinks as its moisture content drops and swells as it rises.

We’ll go into more detail about this in the next section. But, before we do that let’s talk a bit more about how water gets into wood.

Moisture moves through wood as water vapor through the cell cavities (lumens), as bound water diffusing through the cell walls, and as liquid water drawn along by capillary action. You’ve probably seen capillary action yourself.

For example, if you roll up a paper towel and stand it in a glass of water, the water climbs up the towel. That’s capillary action.

How Does Moisture Affect Wood?

Moisture content directly affects wood’s physical dimensions. The give and take of moisture with the surrounding air that we talked about earlier makes wood swell or shrink.

If dried wood isn’t allowed to properly acclimate to the place where it will be used, that give and take will continue even after the project is complete.

This can lead to gaps, buckling, crowning, splits, or other problems, depending on the type of project.

Wood is anisotropic

Anisotropic means that as wood absorbs and releases water, it swells and shrinks by different amounts in its three directions: tangential, radial, and longitudinal (along the grain).

For example, as wood dries from green to oven-dry, it shrinks an average of about 8% tangentially, but only about 4% radially. According to the USDA Forest Service Wood Handbook, tangential shrinkage is about twice the radial shrinkage, and shrinkage along the grain is only 0.1% to 0.2% for most species.

Wood’s density affects shrinkage and swelling

In general, denser woods shrink and swell more with changes in moisture than lighter woods.

Dry wood is stronger than wet wood

As wood dries below the fiber saturation point, most of its strength properties increase. Wood dried to around 12% MC is much stronger than freshly cut green wood, and in some properties, such as compression strength along the grain, it can be nearly twice as strong.

Wood doesn’t like excessive moisture and high humidity

Mold can grow on wood surfaces when the surface relative humidity stays above about 80% for long periods, and most molds grow at temperatures above about 40°F (4°C). Decay is a bigger problem. According to the Wood Handbook, decay fungi generally need wood at or above its fiber saturation point (usually about 30% MC) and temperatures between 50°F and 100°F (10°C and 43°C). Humid air alone won’t wet wood enough to decay; it takes liquid water from rain, condensation, leaks, or contact with wet ground. Keeping wood below 20% MC gives a reasonable margin of safety.

Below about 40°F, high humidity is less of a mold risk, as long as the wood dries out before temperatures rise again.

How Temperature Affects Your Wood Moisture Meter

If you’ve read this far, you have a basic understanding of how relative humidity, temperature, and wood moisture content interact. That knowledge will help you measure wood moisture content accurately in any weather.

Our free Wood H2O app can also help you quickly find the EMC for your project’s conditions, which helps you avoid moisture-related problems after construction or installation.

Now let’s talk about how temperature affects your wood moisture meter.

Pin-type wood moisture meters

Pin-type meters are sensitive to changes in wood temperature because of the technology they use.

Pin meters take moisture content readings by passing an electrical current between the pin tips and measuring the resistance. But as the wood’s temperature rises, its electrical resistance drops, which makes the moisture reading higher.

So for an accurate reading, you’ll need to correct for the wood’s temperature. Most pin meters come with instructions for doing this.

Pinless wood moisture meters

Because pinless wood moisture meters don’t rely on electrical resistance to measure moisture content, you don’t need to correct their readings for temperature, except at temperature extremes.

Relative humidity in the air also doesn’t significantly affect pinless readings unless there’s condensation on the meter. And Wagner’s Orion^® pinless meters use IntelliSense™ technology, which helps keep surface moisture on the wood from skewing readings.

To prevent moisture-related problems in your wood projects, you need accurate moisture readings. And accurate readings depend on understanding how relative humidity, temperature, wood moisture content, and your moisture meter’s technology interact.

If you’re planning a construction or renovation project, also read about moisture content in wood studs.

Shop Orion Moisture Meters

Last updated on October 21st, 2026