Extension Cords & Snow: 5 Common Questions (Answered)

Extension cables are an almost universal staple in tech setups, construction sites, and the average residential household alike.

And, of course, safety is crucial when we are looking at ways to extend power, especially in damp or wet conditions.

For instance, is it safe to run extension cords outside in the snow? Can freezing temperatures make them unsafe? How can you tell what conditions a given cord can withstand?

Well, if you’d like answers to any of these questions, then keep reading, because that is what this article is all about.

Here’s the Truth About Extension Cords & Snow:

In the USA, extension cords rated for outdoor use are designated by a “W” symbol. Outdoor cords are water-resistant, but there is no such thing as an entirely waterproof cable. Cables should not be run through snow; the heat of the cord can melt the snow around it, which could cause a short.

Can You Run Extension Cords Under Snow?

Firstly, let’s explain why it’s usually a bad idea to do this, and why you shouldn’t even think about it unless you know what you’re doing and how to do it safely.

Electrical wires generate heat.

Extension cables are covered by thermal insulation, which keeps most of this heat in, but some heat always escape by radiating out.

• This means that if you run an extension cable under a layer of snow, some of that snow is going to melt and turn to water.
• Outdoor-use extension cables typically are water-resistant, but no cable is completely waterproof.
• Leaving even an outdoor-use cable in contact with water could eventually cause a short, even if it doesn’t happen right away, as the insulation gradually deteriorates.

There are extension cables explicitly designed for use in freezing temperatures, and these cables can be safely used in snowy conditions.

However, they are not intended to just sit outside, exposed to the elements forever; they’re meant to be used only in the short term while you’re actively doing work outside.

In short, if you use the right kind of cable, you can work outdoors in the snow with an extension cable, but you should never leave the cable outside indefinitely.

How do Freezing Temperatures Affect Extension Cords?

Metal is very conducive to heat, and will physically expand when immersed in a hot environment, and contract in a cold one.

With large pieces of metal, such as those used in construction, this is not generally a problem and is taken into account during the construction process.

However, it’s a very different story when we’re dealing with very thin filaments of metal, which is exactly what electrical wires are.

The smaller the piece of metal, the more significant the stress of expanding or contracting will be, and most electrical wires are designed to work in a specific temperature range.

In short, when electrical wires get too cold, they could in fact, contract to the point of snapping and breaking, rendering the wire useless and incapable of transmitting electricity.

This is one of the purposes of those rubber layers of insulation that extension cords always have (the other purpose is to keep the electricity inside the wire).

The insulation, true to its name, helps to prevent too much heat from leaving the wires, keeping them within the desired temperature range during use.

However, no insulation is perfect, and different types of cables are designed for different temperatures.

If you are working with extension cables in below-freezing conditions, you should be using a cable specifically designed for use in cold weather.

Such cables have heavier-duty insulation that will more effectively keep the cable from getting too cold, and prevent cold-related breakages.

Do Extension Cords Work When Covered in Snow?

If the cable in question is rated for outdoor use in freezing temperatures, then it will probably work properly if immersed in snow, for at least a while.

But even heavy-duty extension cords are not designed to simply be left out in the cold forever; they will work for a while, but not indefinitely.

If you leave the cable immersed in snow for days on end, sooner or later, one of two things—maybe even both at once—is going to happen: an electrical short, or a wire breakage.

Outdoor-use extension cables are water-resistant, and cold-weather cables are cool to cold-weather-resistant.

However, no cable is completely weatherproof, and if you leave it outside long enough, eventually, something bad will happen.

If you’re lucky, it will just break and stop working, without causing any further harm.

If you’re less lucky, it could cause a dangerous and costly electrical fire.

Suffice it to say, while an extension cable can be covered in snow in the short term, do not leave it like that for any longer than you need to.

For a more in-depth look at extension cord safety, check out our 5 Easy Rules for Extension Cord Safety.

How Do I Know if an Extension Cord Is for Outdoor Use?

Thankfully, there is a standardized marking system for extension cables in the United States that will tell you what uses they are rated for.

When purchasing a cable, its intended use cases should be indicated on the packaging.

However, if you threw the packaging away and forgot what it said, you can get answers from the markings directly on the cable’s insulation.

A “W” marking indicates that the cable in question is rated for outdoor use.

However, there are several useful indicators to know, so as long as we’re on the topic, let’s outline a brief list of them:

• Cables marked with an “S” indicate a general-use rating.
• Cables marked with a “T” indicate the presence of vinyl thermoplastic in the insulation.
• Cables marked with an “O” indicate oil-resistant coatings.
• Cables marked with a “W” indicate an outdoor-use rating.
• Cables marked with a “P” indicate parallel wire construction.
• Cables marked with an “E” indicate the presence of thermoplastic elastomer in the insulation.
• Cables marked with a “J” indicate standard 300 voltage insulation.

Sadly, there is no standardized marking to indicate a cold-weather-rated cable, but this information should be indicated on the cable’s packaging.

Can Extension Cords Freeze and Get TOO Cold?

Metal contracts in the cold, as the metal molecules get closer together and cause it to take up less space.

When electrical wires contract in this manner, because they are comparatively thin and fragile, this “shrinking” effect can actually cause them to break.

This is what is actually meant when it’s said that an electrical cable can “freeze.”

In other words, the wire can contract due to cold, and break as a result.

And, of course, when the wire snaps, the electrical flow is interrupted, and the wire can no longer do its job of moving electrons from point A to point B, making it effectively useless.

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