does rain increase indoor humidity

Many people know that humidity rises as rain rolls in. With a quick step outside you can feel the difference, but does rain increase indoor humidity?

The short answer is yes; rain increases indoor humidity.

With rain comes humidity, and for many people that spells trouble. 

Curly-haired folks can expect a bad hair day and people with arthritis have a little extra discomfort, but that’s not the only issue with high humidity indoors.

As rain falls, it evaporates and adds water vapor to the air, increasing the humidity. Since you can’t keep that air outside, the humidity levels in your home rise as well.

Why Does Humidity Rise When It Rains?

why humidity rise

While humidity is a common term, not everyone knows what it means.

Even if you don’t know how to explain it, you probably know the feelings that come with high humidity.

The air can feel thick and sticky wherever you go. That thick feeling comes from excessive water in the air.

What? How does that work?

Water might be most recognizable as a liquid, but it can freeze into ice or evaporate into a gas.

The gaseous form is known as water vapor, and it can hang in the air giving it that dense feeling we know and love.

Humidity rises as water vapor overloads the air. If the humidity climbs too high, it prevents other moisture from evaporating.

But, Why Does Rain Increase Indoor Humidity?

why rain increase humidity

When you walk outside during, before, or after a rainstorm, you will likely notice that the air feels different.

You might notice that your sweat doesn’t evaporate and leaves you feeling sticky.

If it rains enough and fills the air with too much water vapor, there’s no room for anything else to evaporate, including sweat.

While the effect is most apparent outside, it also occurs indoors.

Since you can’t completely seal a building to prevent air from moving in and out, the humid air works its way inside.

What Affects the Humidity Levels?

affects humidity level

Did you know that there are different ways to discuss humidity in the air?

Absolute humidity is an exact measurement of how much water vapor exists in the air.

Also known as specific humidity, it appears as grams of water vapor for each cubic meter volume of air.

It’s a technical measurement but doesn’t account for air temperature.

Relative humidity refers to the percentage of water vapor in the air. 

High humidity percentages indicate a higher saturation of water vapor in the air.

Warmer air holds more water vapor than cold air, so you notice the sticky, sweaty effect in summer more than in spring.

Another way to discuss humidity is the dew point. The dew point refers to the temperature the air needs to reach to achieve saturation.

Once the air drops below the dew point, the water vapor condenses and leaves droplets behind.

Tip: Remember two important things. First, a high relative humidity means there is a lot of water vapor in the air. Second, a high dew point means the air can hold more water vapor. 

How Is Humidity Measured?

measure humidity

Relative humidity is a metric that is measured and calculated by how much water vapor is in the air.

This is measured in a range of 0-100%, and humidity levels will be expressed in percentages.

On a severely dry day in a dry climate, such as the desert, the humidity will be at 0%.

On a wet and rainy warm day in a humid environment such as a rainforest, humidity could be at 100%.

People use hygrometers to measure humidity. Meteorologists use the device to determine how much moisture is in the air at any given point.

There are several different types available depending on how precise somebody needs to be and their preferred approach.

Most homeowners opt for easy-to-use digital hygrometers that take readings and display them on digital screens. They are relatively easy to find at a home improvement store, big-box store, or online.

Note: Some thermostats actually feature digital hygrometers to make your life easier.

How Does Humidity Work Indoors?

how humidity work

You can see evidence of the outdoor air dropping below the dew point outside.

You might notice droplets of water on the grass and other surfaces, but what about inside?

The dew point doesn’t apply to outdoor air. Every building needs to regulate the amount of water vapor in the air to prevent it from reaching saturation.

While it’s not going to rain in your house as it does outside, once the air can’t hold any more water, it has to go somewhere!

Water droplets on large surfaces, including your basement walls, can indicate a problem.

Condensation inside indicates a moisture control issue that can cause a range of issues.

Excessive indoor humidity can create mold and mildew, damaged walls and furniture, instigate allergies, and even ruin the brickwork and coverings.  

Note: Don’t freak out if you notice a little condensation on the side of your glass of ice water, that’s normal and doesn’t indicate excessive humidity.

What Is the Best Indoor Humidity Level?

best humidity level

The ideal indoor humidity level is around 30-40%. Less than that may dry out your skin or impact your health by causing dry noses or throats.

More than that amount of moisture can cause mold in the home, which will lead to serious health consequences.

Can You Regulate the Humidity in Your House?

As we have discussed, rain can increase indoor humidity.

But, that doesn’t mean there is nothing you can do to lower your humidity levels to avoid any negative impacts on your home or your health.

It’s a good idea to pick up a hygrometer to track your humidity levels. 

Once you get an idea about your humidity levels, it’s easy to figure out how to regulate them.

How To Decrease Humidity in a House

decrease humid in house

Areas that see a lot of rainfall might have issues with moisture buildup in their homes.

Thankfully, there are some handy appliances and tricks to pull excess moisture from the air and keep humidity levels in check.

  • Utilize your HVAC system’s settings
  • Be sure to change your air filters
  • Clean debris from your HVAC unit
  • Use a dehumidifier

Running the heat or air conditioning naturally dries out the air, making it a helpful option for people dealing with temperature and moisture issues.

It also reduces the amount of outdoor air making its way inside because you close up the house when running the HVAC system.

Keep in mind that maintaining your HVAC system and air filters is crucial to your home health.

Also, you should always have proper ventilation systems and keep your home at an appropriate temperature.

Note: Make sure you watch for signs of increased moisture in case you need to make adjustments.

How to Increase Humidity Indoors

increase humidity

It’s important to note that some places struggle to reach saturation and even maintain a healthy level of water vapor in the air.

Dry climates might need to add moisture to the air inside because there’s so little water around. Installing a humidifier is the best solution.


Rainy days can ruin outdoor events, cause bad hair days, and even leave you feeling less than your best but does rain increase indoor humidity?

Yes, rain can increase indoor humidity.

Typically, light rain won’t increase the humidity in your home, but at a certain point, excess rain will cause your home to have more humidity.

It’s common to experience high humidity in a house after rain, especially in a heavy storm.

High humidity levels in a house can have significant negative impacts on the building and your family. 

Thankfully, it’s easy to monitor humidity levels and there are devices to help regulate the water vapor in the air.

Now, you’re ready to handle this situation head-on and ensure that rainy days don’t impact your health or your home’s structural integrity over time.