Storing Firearms/Ammo in Home vs Garage

I'm moving from Arlington to DC in about a week and leaving my firearms and ammo with a friend. The firearms will be in a locked foot locker, and though I couldn't say it was airtight, it's pretty close. Ammo will be in the same footlocker and ammo cases. He has two places I could store them in his detached garage, which I think he'd prefer or a storage room in his basement that used to have mold issues but thinks it's resolved.

My questions are: are there any issues or drawback in storing the firearms and/or ammo in the detached garage where the temperature will go up and down all the time and maybe be humid at times? And should I care at all about the potential mold issues, with a sealed foot locker? The handguns will be in cases inside the locker as well.

Thanks for an info you can provide.

You could get some kitty litter, pour it into a coffee filter, staple it up. You got yourself a cheap and easy way to keep moisture out of the ammo. Leave one of those in each ammo can. I've been fine after leaving it to sit 5 years ago and shooting it this year.

1 teaspoon or tablespoon. You don't need much.

Spray it down with something like Eezox. It's a cleaner/lube but it dries and will protect better than anything else.

Google "eezox salt spray" and you can find several pictorials of how well it protects against corrosion.

Add a desiccant bag and it will be ok for a long time.

Have you considered renting an indoor (climate controlled) storage space? When I lived in Arlington & DC I rented at the (forgot the company name) in Ballston.

I wiped gear grease on my bluing and wrapped them in newspapers, inside a cardboard box.

It really comes down to their value and what you're willing to pay to preserve them.

Hey mate, just like this powerful statement, "store in a cool dry place". That is all. Make sure your friend place them where the temperature/weather won't damage them (Ammo/Firearm) either. Cheers on your re-location to DC, may your move bring you fortune.