Why Is the Humidity in My House So High After It Rains?

If you live in an area that gets a lot of rain, you may have noticed that your house often gets significantly more humid shortly after it rains. You might be wondering how normal this is, or if there is perhaps something wrong with your home.

It’s totally normal for your house to be more humid after a rainstorm. This happens because, after a rainstorm, the rain evaporates and transfers its moisture content to the surrounding air. The warmer it is outside, the faster the rain will evaporate, and the more humid it will become.

That being said, while some level of increased humidity in your home after a rainstorm is normal, you should pay attention to whether your humidity levels get too high after it rains, as this may be a sign that water is leaking into your home from somewhere.

Related: Does Outdoor Humidity Affect Indoor Humidity?

In this article, we’ll be sharing with you what you need to know about humidity in your home. We’ll be taking a closer look at the relationship between rain and humidity, and we’ll also show you how to recognize when there’s too much humidity in your home and what you can do about it.

Humidity 101

Before we get into more detail about humidity in your home, it may be helpful for you to have a basic understanding of how humidity works and how rainfall affects it, if you don’t already (if you do, feel free to skip this section of the article).

When rain falls, it increases the relative humidity of the surrounding air because the rain evaporates and saturates the air with water vapor. The term “relative humidity” refers to the percentage of moisture in the air relative to the air temperature. This is different from absolute humidity, which is a measure of the actual amount of moisture in the air.

Because warm air can hold more moisture than cold air, this means that for any given amount of absolute humidity in the air, the relative humidity will be lower if the air is warm, and higher if the air is cold.

You may have also heard references to the “dewpoint” at one time or another. The dewpoint is a measurement of what the air temperature needs to be relative to the absolute humidity in order for the air to become saturated (the point at which the air reaches the maximum amount of moisture it can hold).

Therefore, a low dewpoint temperature means that there’s not much moisture in the air, while a high dewpoint temperature means that the air is really humid. 

Why Is Too Much Humidity Bad For Your Home?

Aside from just making things uncomfortable, having too much humidity in your home (especially for prolonged periods of time) can damage your home and even present a health hazard. If you let the humidity in your home go unchecked for too long, you’re putting yourself at risk for the following problems:

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Growth of Mold

If you let your house stay too humid for too long, one of the first things that will happen is that mold will start growing. Mold loves warm, damp conditions, and it’ll be more than happy to start spreading throughout your home if the conditions are right.

Related: How to Prevent Mold in Window Air Conditioner?

At best, the presence of mold in your house will simply cause an unpleasant, musty smell. In more serious cases, however, inhaling mold spores can trigger allergic reactions in people with asthma or other allergies, and in the worst cases, mold will eventually start destroying any soft surfaces is it growing on.

Rotting Floors, Furniture, and Other Wooden Materials

Anything that is made of wood in your home will start to break down if it comes into contact with moisture for a long period of time. This includes your floors, wooden furniture, and other fixtures like window frames and doorframes.

In mild cases, wood that has become waterlogged will appear discolored and may feel slightly soft. In worse cases, however, moisture can cause wood to rot, causing irreparable damage.

Poor Air Quality

Having high levels of humidity for long periods of time can seriously decrease the air quality in your home. Aside from providing a breeding ground for mold, high humidity also promotes the growth of dust mites, which can cause allergic reactions in some individuals.

In addition, some building materials used in houses start emitting harmful chemicals when exposed to prolonged heat and moisture, which can potentially cause respiratory issues.

Damaged Paint and Wallpaper

If the humidity in your home remains high for a long time, your paint and wallpaper are going to be among the things that are the most affected. This can happen to either interior or exterior walls, although it’s usually worse on exterior walls since they tend to come into contact with humidity a bit more.

High humidity certainly can affect the paint and wallpaper inside your home though, causing your paint to flake off or your wallpaper to start curling up from the wall. 

Damaged Brickwork

In most cases, the exterior walls of houses are sealed up to prevent humid air from getting beneath the surface, but some amount of moisture often gets in regardless. If enough moisture makes its way into the brickwork, it can cause the mortar holding the bricks together to swell up and crack.

If your brickwork is frequently subjected to changes in humidity, this can cause your bricks and mortar to start cracking and crumbling, due to the constant expanding and contracting it will experience.

Bug Infestations

Many types of insects, including the aforementioned dust mites, thrive in humid conditions. This is because the humidity provides them with an ample source of water for them to sustain themselves on. 

High levels of humidity can attract a variety of insects to your home, including springtails, crickets, and even pests like ants and cockroaches.

Humidity-Related Health Issues

High humidity levels can be quite uncomfortable, of course, but they can also be dangerous too. When your body gets too hot in normal cases, it starts producing sweat. As your sweat cools off and evaporates, your skin is cooled off in turn.

When humidity is really high, your sweat doesn’t evaporate as easily, and your body will attempt to compensate by producing more sweat. Sweating causes your body to lose water, so the more you sweat, the closer you get to dehydration.

High humidity can also make it harder for you to sleep, which will, of course, lower the quality of the sleep you do get and leave you feeling more fatigued than normal.

How Do I Know if My Home Is Too Humid?

The ideal relative humidity in your home should be between 30-50%. You don’t want to have too much humidity in your home, but you also don’t want your home’s air to be too dry, as this can cause dry, cracked skin and generate excessive amounts of static electricity in your home.

If you want to find out what the specific measurement of humidity is in your home, your best bet is probably to get a hygrometer. You can find both analog and digital hygrometers, and both types are usually fairly inexpensive to buy.

If you don’t want to buy a hygrometer, there are several ways you can check for high humidity levels in your house without one:

  • Look for places where water is visibly condensing. This usually happens on windows, mirrors, pipes, and other surfaces that are generally a bit cooler.
  • Look for discoloration or stains on your ceiling and walls.
  • Take notice if the floors, walls, and other wooden objects in your home feel damp or soft.
  • Look out for the smell of mildew. If you’re having trouble detecting any unusual smells in your home, try stepping outside for a few minutes and then returning. 
  • Take notice if you or other members of your household are displaying any allergic symptoms like wheezy breathing or a chronic cough with no clear cause. 

How Do I Deal With High Humidity in My Home?

Fortunately, there are a few things you can do to deal with high levels of humidity in your home. These things are:

Use Your A/C

Air conditioning systems work by removing moisture and heat from the air and sending the cool, dry air inside while venting the heat and moisture outside.

Related: How Long Does an AC Take to Cool an Apartment?

If you have central air conditioning in your home, running it for a little while will solve your humidity problem.

Make Sure Your Home Is Properly Ventilated

For any areas in your home where there is typically more moisture present, such as bathrooms, kitchens, and basements, you should ensure that these areas have adequate ventilation.

This will help you eliminate excess humidity from these areas when you need to.

Make Sure Your Home Is Properly Insulated

A home that is properly insulated will not only keep your home warmer in the winter but cooler in the summer as well. By making sure everything is sealed up, you can keep the temperature in your home more consistent and also keep excess humidity out.

Related: Why Is My Room In The House So Hot At Night?

To that end, you should make sure that your walls and ceiling are properly insulated, and that your home’s doors and windows are sufficiently sealed with weatherstripping.

Invest in a Dehumidifier

Dehumidifiers, as the name implies, are used specifically to eliminate the humidity in an enclosed area. If the humidity in your home is really a problem for you, a dehumidifier may be your best bet. 

You can buy dehumidifiers that remove the humidity from a single room, but you can also find whole-house dehumidifiers that can remove the humidity from your entire home. Most of these whole-house dehumidifiers work by connecting to your HVAC system, but some function as portable, standalone units.