We are in a rental house while we build our house. Unfortunately it's small and the only place I have for my safe is in the garage. My monitor is telling me he safe temperature is dipping into the high 30's with a current temp of 39 degrees and 29% humidity. Is that cold enough that I need to move my guns inside, or will they be OK the the low humidity? I'm worried about moisture and rusting.

Do you have a goldenrod type heater/dehumidifier in the safe? If you do I think you're ok. If not, you had better keep an eye on them.

I don't, but I will look into it. 29% humidity at 39 degrees equals a dew point of 9.5 degreesF. So the air is still dry, but it's cold in the safe. From what I have read, a golden rod won't raise the temperature inside the safe a whole lot. Is that true?

Pop a coffee cup warmer in there with a cup of water, ....will bring up the temp and humidity.

Being cold in and of itself should not cause issues. Rapid temperature and humidity change can be a real problem. Don't bring them inside and walk away or you will induce a rusting problem. Cold metal brought into a warm environment will condense any moisture in the air like a glass of ice water. If you don't remove metal from stock, dry it out and let it stabilize and re-oil, you will end up with issues.

When on the farm, the truck guns stayed in the truck. Carrying them inside and outside would get them rusting quick.

I don't believe the dew point has anything to do with inanimate objects. The temperature will still be the same.
Putting a warm liquid in there is asking for rust as it will condense on the metal.

I think that you will be fine as long as you have a golden rod-type device in the safe. If you want to bring a cold gun into the house to admire it, slip into a soft case before you bring it in, and leave it in the case until it warms up.

Re-read your posts, maybe you will not need the golden rod this winter. But I would get one anyway, I think.

Mid to high 30's and 29% humidity sounds like the perfect storage environment.
JR

I believe that temperature and humidity will be OK but I would keep an eye on it. I keep a dehumidifier next to my safe in the basement and keep the humidity near the safe at less than 45%.

You could also contact Cortec Corporation in St. Paul, MN. 651-429-1122. They make vapor phase corrosion inhibitors that I have used in other industries. I believe they have inhibitors that can be used in safes and corrosion inhibitor bags designed for military weapons.

No! Do not follow this advice. You are trying to keep your guns from rusting. This might be a great idea if you were attempting to turn your safe into a damp box for rust bluing or browning. Put a Goldenrod in there, and you'll be fine.

Get the largest Goldenrod you can fit in there across the bottom and be done with it.

Amen. I have a very big safe that has been in an unheated space for at least 15 years. I put the biggest Goldenrod I could find in it when I got it and it has withstood temperature shifts from 100 down to about 14 degrees each year for all that time. Regardless what the outside temp is I can open that safe and the contents are warm and dry, with not one speck of rust over those 15 years. With the Goldenrod in there you can just fuggedaboutit.

SRH

Thanks guys. I'm going to stop by Cabelas on my way home from hunting today and look at the golden rods. I brought two guns in last night and with it being so dry here in CO, I believe it would be fine but I think I'm going to throw a golden rod in it just in case.

Not correct. By definition the dew point is the temperature at which water vapor in the atmosphere will condense to form liquid dew. If the temperature in your gun safe reaches the dew point liquid dew will form on the firearm and rust may form on any iron based metallic parts, including internal parts.

Siberian trappers and professional hunters NEVER take their guns inside, even when temperatures drop to -40C. The guns are hung on pegs outside the hut. Cold won't harm a gun. Rapid changes of temperature will (like someone said before).

That coffee cup suggestion would be an excellent way to go if you want rusty guns and a safe full of the nastiest fungus/mold you've ever seen or smelled. Warm, dark and wet.....great for mushrooms too. I've seen it.

Goldenrod hands down.