It sounds simple, but how warm you need to keep your garage depends on what you plan on doing in it.
If you’re just using it for storage or to park your car, that’s going to have different temperature requirements than if you’re using it as a workshop, right?
It turns out that those scenarios have more in common than you might thing.
What temperature should you keep your garage at? It depends on how you use your garage and where you live. A good rule of thumb is to always keep your garage above the average dew point so condensation doesn’t form. This is usually around 40°F for inland states and around 65°F for coastal states.
Those are just guidelines and obviously the specific temperatures can vary greatly depending on where you live.
Let’s look at the two main factors in a little more detail to give you a better idea how we came up with those numbers.
Factor #1: Raw Temperature
Your car and your power tools both have rechargeable batteries, and those batteries have a range of temperatures that they work best in. If you go outside that range, the battery loses juice and it just won’t work.
Then you’re stuck in a parking lot waiting for AAA to come, right?
Different batteries have different operating ranges. Lead-acid car batteries work between –20°C and 50°C (–4°F to 122°F). The Lithium Ion (Li-ion), Nickel Cadmium (NiCd) and Nickel Metal Hydride (NiMH) batteries work between 0°C and 45°C (32°F to 113°F). (source)
Outside of those ranges, it can actually be harmful to charge the battery, shortening its lifespan.
Temperature also has an effect on the duration of the charge.
Battery University has some VERY science-heavy articles that go into the details, but the important thing is that “Cold temperature increases the internal resistance and lowers the capacity. A battery that provides 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at –18°C (0°F).“
You want your garage temperature to stay within that range, but I’ll admit that’s a pretty big range.
Lets look at the second factor to help narrow it down.
Factor #2: Dew Point
You’re probably wondering what the dew point has to do with your garage.
Just hear me out.
According to the National Weather Service, dew point is the temperature at which the air cannot hold any more moisture and relative humidity is at 100%.
As the temperature drops below the dew point, moisture comes out of the air as fog or condensation. Little droplets of water start to form on anything that isn’t covered – like your tools and those boxes stacked in the corner of your garage.
Metal will rust. Mold and mildew start to form. Wood starts to warp. Etc.
Ideally, you should keep your garage temperature above the dew point so the moisture can stay in the air where it belongs.
Average dew points in the winter in the United States range between 50°F to 65°F in coastal states and between 15°F to 40°F in the interior of the country. Obviously the farther north you go, the colder the dew point will be.
Weather.us has an interactive map that lets you zoom in on a location and see your current or historical dew points. I’m a bit of a data geek, so that kind of thing is really cool to me.
Bonus Factor: Human Comfort
Here’s a bonus factor, and it’s by far the least scientific of the three.
What temperature range are you comfortable in?
If you’re going to be in your garage for any length of time. you want the temperature to be warm enough. The World Health Organization (WHO) defines the warmth of human comfort at 18°C (64°F) for healthy adults that are appropriately dressed (pdf source).
Even if they’re not exposed to the elements, winter temperatures can be rough on your car, your tools and anything else you store in your garage.
I recommend reading these articles because they’ll help you take more control of the temperature in your garage in the winter.