My wife and I have recently moved into a fairly "wet" winter environment. (Wet fog and drizzle daily.) As we are not completely settled, my gunpowder has been relegated to storage in less than an ideal place.
The powder is safe and dry, (indoors but subject to out door temps - garage) but I am curious about what affects the cool/cold humid ambient air of winter will have on it, if any. I have both black and smokeless, some of it has been opened, most of it has not. Will the powder draw moisture from the air?.... enough to cause problems?

Thanks,
Hayseed

As long as the caps are tight on the cans and the cap gaskets are in place there is nothng to worry about.

Alk8944,
Thanks for the reassurance.
This is one, wet, winter environ. No snow, so I'm told, but it's the only placed I've lived where folks wash their vehicles on a regular basis in the wintertime. Not so much because they're dirty, but to keep the moss off!

Hayseed

Humid here and usually fairly warm, as alk8944 says as long as the caps are tight no problem. Rust is a big problem though so I have to be very careful with dies and anything “rustable”. I ended up partitioning off a portion of the garage and keep a dehumidifier running there.
On general principles I do not leave powder uncapped, or in the powder measure, except when using it.

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Ipsis Rebus Dictantitbus

I just read this thread-link on another forum. Make sure you read the posts by Iowegan. He is outstanding.
Funny thing with Lee dippers - Ruger Forum
Sonny

I live in S. Central TX and humidity is a problem mmost of the year. I keep my powder cap tight but as added insurance, I buy disiccant packets and put them in the powder.

Keep one in the die boxes also and closed tight.

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Slim, U.S. Army, Ret.

Hayseed, as others have said, in securely closed containers you should have no problems. When you want to use it for reloading I suggest you bring it into the house and let it get up to room temperature.

Thanks for the good info everyone!
I appreciate your time and comments.
Not having to replace a bunch of powder eases the strain on my reloading budget.

Hayseed

I know that the OP wanted general info, but one other item is worth mentioning: Some powders are more hygroscopic than others. For instance, my favorite handgun powder, SR-4756, is highly hygroscopic. Even though I live in a normally very dry climate, I never leave 4756 in a powder measure even overnight. Viht handgun powders, I've learned, are not very hygroscopic at all. I've left N-350 in a measure with a fairly loose cap for weeks, with no noticeable absorption of moisture, even though I don't recommend it.