How Are Rain And Humidity Related? Does Rain Increase Humidity?

Rain is a common weather condition that not everyone enjoys. While we know it will add water to the ground, many of us are unsure whether it will increase or decrease humidity.

In general, the relative humidity will increase locally in and after the rain due to the evaporation of water. However, rain can decrease the humidity on a large scale by depositing water vapor in the ground through condensation. 

This post will walk you through more details about the relationship between rain and humidity. You will also understand what to do if it rains. 

What is the humidity?

There are two metrics to describe how humid the air is: absolute humidity and relative humidity. 

Absolute humidity refers to the actual amount of moisture in the air, whereas relative humidity presents the degree of saturation of the air, which is expressed as the percentage of the amount needed to achieve saturation at the same temperature.

In addition, the warmer the climate, the more water vapor the air is able to hold.

Between these two metrics, we use relative humidity more often.

What is the humidity when it rains?

humidity when it rains

Because water vapor in the air can only turn to liquid when it is saturated, many people believe that when it rains, the humidity of the air is 100%.

This is not correct. When it rains, the humidity outside ranges from 90% to 99%, rather than 100%.

This is due to the accumulation of water vapor in the cloud. When the air in the clouds becomes saturated, rain forms and falls to the ground.

That is, the humidity in the cloud is 100%, but not in the ground air.

Does rain increase outdoor humidity?

After a rain, you may notice that the air is clammy and your skin is sticky. This is due to the fact that rain increases outdoor humidity.

Depending on the weather and how heavy the rain is, the outdoor humidity can vary to varying degrees.

When the rain hits the ground, the ground will fill up with water. A proportion of water will evaporate and get into the air. The humidity will increase when more water vapor gets into the air.

However, it only increases the outdoor humidity level in your area. When you look at the weather on a large scale, you can see that the moisture level decreases after the rain because the water vapor that used to linger in the air has turned to rain and falls on the ground. Not all water particles can quickly re-enter the atmosphere.

Does rain increase indoor humidity?

Rain will not enter our homes directly as long as our houses are in good condition. Outdoor humidity, on the other hand, has an effect on indoor humidity.

This is because moisture can enter the room through windows, doors, and any other crevice in the house. As a result of the rain, indoor humidity will rise.

However, the effect of rain on indoor humidity levels varies greatly. If your home has good insulation and you keep the windows and doors closed while it rains, this could be an indication of water damage.

What to do if your room is too humid after it rains

High humidity can attract bugs and promote mold and dust mite growth. It can also rot furnishings and frames, jeopardizing structural integrity.

If you live in a rainy area, you should take precautions to deal with the moisture caused by the rain.

Keep windows and doors closed

People like to open windows and doors to get more fresh air. While it is not a problem on sunny days, it is not a good idea when it rains.

It is best to keep windows and doors shut during and after rain. This prevents the most humid air from entering the house. After a few hours, you can reopen them.

Upgrade the insulation 

In humid climates, good insulation can keep your home not only warmer but also drier. It can also ensure that there are fewer cracks and crevices through which moisture can enter.

Nonetheless, installing new insulation may be costly at first. You can experiment with different methods before deciding whether or not to proceed.

Run a dehumidifier

A dehumidifier is a device that reduces humidity levels. It has the ability to remove excess moisture from the air, which is the opposite of what rain does. You can choose the appropriate size based on the humidity in your home after the rain.

Because moisture can get into every corner of your house, you should consider installing a whole house dehumidifier to combat the rainy climate more effectively.

Use an air conditioner 

The rainy season is frequently accompanied by a hot climate. If this is the case, you can use an air conditioner to extract extra moisture while also cooling you down.

If your house is still humid even with the AC on, your unit could have a problem. Or simply because your air conditioner can’t handle the moisture. You can try running a dehumidifier along with an AC to solve the problem.


This post has discussed the relationship between humidity and rain. Because rainwater evaporates, it can add moisture to the air and raise the humidity after it rains.

Don’t dismiss the effect of rain on you. It can cause mold, dust mite growth, and damage to your furniture and home.

To combat the high humidity caused by rain, use a dehumidifier, an air conditioner, or improve the insulation. The most basic method is to close the windows and doors.

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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