Houston, I have problem.....
. Just kidding.
When/if I get my reloading set up again, it will be in my garage, with slab heat and a dehumidifier. Everything is out there now in storage, anyway.
Temps range from about 53 to 60 in winter, ( I keep the thermostat turned all the way down) the commercial grade dehumidifier is set at 70%, the powder is in sealed containers. No air condtiuoning, so in warm weather (such as it is here), inside temps might get a bit higher, but not much.
With some variance - I just turned both the boiler and de-humidifier off for the summer season - the temp won't vary much, tho the humidity will pretty much follow ambient.