What Causes Container Rain?

#Shipping Containers • February 26, 2018 • 2 Likes

From New York to California, the United States has shipping ports and harbors in every major coastal city all over the country. With the Continental U.S. having a coast on both the Atlantic and Pacific oceans, maritime shipping has established itself as an essential part of the economy and workforce.

The U.S. Maritime industry is one of the largest in the world, second only to China in exports. Since over half of all imported goods are transported by vessel, water transportation contributes roughly $36 billion U.S. dollars and 64 thousand jobs to the U.S. economy annually. The overwhelming majority of goods shipped on vessels are containerized. With so many precious goods and cargo coming by sea in shipping containers, there’s high demand for loss and damage prevention.


Every year, millions of dollars’ worth of cargo has to be destroyed or thrown out due to moisture damage incurred during transit in shipping containers. Approximately 10% of all containerized goods are discarded due to moisture-related damages. This issue has been a huge problem in the maritime industry for a long time. In a study released by the UK P&I Club, it was reported that 25% of damage is physical and 14% is temperature related.

What is Container Rain?

Have you ever forgotten a water bottle in your car on a hot day? When you get back you see that water droplets have begun to climb up the walls of the bottle. The same process that’s occurring in the water bottle can also happen in shipping containers—on a much larger scale.

Container rain is caused by moisture. Most shipping containers are loaded near the ocean where the air has a higher concentration of water. The moisture in the air gets trapped in the container. As the air in the container settles, the moisture condenses in colder areas of the container. When the container heats up again, the condensed water expands and rises to the top of the container, clinging to the walls and ceiling. The moisture on the walls is known as container sweat.

As temperatures increase, the moisture climbs up the interior of the container before dripping down—this is what is commonly referred to as container rain. Should container rain drip into cargo, moisture-sensitive goods may begin to grow mold, while other cargo can be permanently damaged or destroyed due to warping and corrosion.

International Shipping

When cargo is transported through international supply routes, shipping containers experience radical temperature and climate fluctuation. Temperature change can be caused by the sun going down overnight or an unexpected cold front. This kind of exposure can lead damaged goods. Unless a container is vacuum-sealed, it’s going to trap some moisture inside. If your goods are loaded in a humid or tropical location like Australia or Hong Kong, the increased moisture in the air will get sealed in the container. This will develop into condensation as the crate makes its way to its destination. Even in colder climates like Alaska, moist air can become trapped in the container and cause severe damage. As the crates move further south the dense concentration of water in the air will expand and evaporate. This makes shipping from colder to warmer climates one of the most high-risk and expensive endeavors.

How to Keep a Shipping Container from Sweating

There are a number of ways to prevent container sweat, each with their own strengths and weaknesses. Some methods are universal and some are climate-specific. Here some ways to prevent damage and keep goods safe and protected from moisture.

• Use Hard Plastic Pallet Crates Rather than Wood.
Wooden pallets can absorb and hold moisture. If a storage container is loaded close the ocean or within a humid climate, the wooden pallets will be exposed to ocean air, which is rich in corrosive minerals and moisture that can lead to severe mold buildup during transit.

• How to Keep Moisture out of Storage Boxes
Cardboard is cheap and readily available in large quantities. The majority of food products that are shipped internationally are stored in cardboard boxes. However, cardboard is extremely absorbent and sure to cause mold during international shipping. If you plan on shipping items or goods in storage boxes, wrap them in plastic in a dry place before loading them into the shipping container.

• Desiccants
Relative Humidity (RH) is a percentage of how much moisture the air holds, as compared to the maximum amount of moisture air at that temperature can hold. A desiccant is a hydroscopic substance used as a drying agent that can drastically reduce RH. Have you ever received a package or opened up food goods to find a small package full of what look like little plastic balls? These are miniature desiccant packets to hold and retain moisture in their packaging. A much larger version of those little packages can be hung from the ceilings of shipping containers to trap and hold moisture. This can be one the best and most efficient ways to prevent moisture damage and control RH levels.

• Dehumidifiers and Air Conditioning
This can be one of the more expensive and complicated methods of protecting shipping container goods. If a container is going to be shipped for an extremely long time or distance, dehumidifiers can be a good option. One potential issue is the need for a constant power supply and the ability for the water to be emptied out on a regular basis. A hose or plumbing line can be hooked up from the outside to drain off the ship but setting it up can add to utility and labor costs.

• Insulation
Insulation is another cost-efficient and effective way to control the climate inside of a shipping container. Lining your shipping container can help control the temperature inside and prevent water condensation by distributing heat. Liners keep the internal temperature above the dew point. If the weather conditions outside of your shipping container are extremely moist you might want to double up on protection with desiccants.

• Ventilation
Ventilation prevents condensation by matching the outside temperature of the shipping container with the inside. Warmer air is pushed out of the container as cooler air comes in. This method can be risky if you are dealing with a humid climate or unpredictable weather patterns.

• Insurance
You can buy insurance for your shipping container and the goods inside. The cost of the insurance is going to vary from product to product. If your company is shipping expensive machinery or electronics for an important client, it might be a good idea to have the shipping container insured. If you pack and protect your containers properly and the cost of the contents aren’t exceptionally high, insurance will more than likely be an unnecessary expense.


The need to prevent container rain doesn’t just stop at vessel shipping. Once the shipping container makes its way off the dock it can be transported one of two ways: trucking or freight. Trucking makes up the majority of domestic shipping and has some unique problems. For example: you might be shipping bananas from the Dole plantation in Hawaii to San Diego, California. Only when the shipping containers arrive, one is headed for Colorado—in the middle of winter. It’s never a bad idea to have your container lined and prepped for their final destination during the initial container loading. With goods that spoil, prepping for domestic shipping is essential to preventing loss and damage.

Freight Shipping

According to the U.S. Census Bureau, freight shipping has increased steadily over the last 15 years as the population has increased. Every day, 5 million tons of goods are delivered via the U.S. railway system. Freight and railway make up almost half of all domestic shipping. Damage from freight shipping occurs mostly due to temperature change. With the majority of the U.S. railway system in the south, products coming from cooler climates are exposed to rapid heating from the warmer southern climate.

Do You Need Shipping Container Protection? Choose Eurolog Packing Group

Eurolog Packing Group creates and designs a comprehensive range of quality of packaging solutions to protect cargo from all types of damage. Our goal is to find the best way to deal with problems that arise during cargo shipping. We provide a range of products and systems that improve the international transport of goods. Our absorbent blanket-desiccant and bag-absorbent pads are proven to reduce the RH levels in your shipping containers. If you know your container is going to go through radical temperature change, be sure to take a look at some of the thermal liners and blankets we have to offer. You need to insure that your goods and products are going to arrive safe—we can help.


Want to learn more about how our products can protect your cargo?



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