I have posted this before, and I know a few will debunk me, but I store all my powder and primers in a fridge. The temp is constant all year round, except recently when we had temps near 50 degrees C, and no fridge was working well.
A 'Cooler' also works well, the type with a sealed top lid is best.
I've had people say that this is a bad idea because moisture will form on the inside of the containers when brought into a warm environment, but this is not true, moisture forms on the OUTSIDE of the container but not on the inside.
As long as you keep the container sealed in between loading your powder measure and dumping any unused powder back into it, it will be fine.
Another thing I noticed is that velocity is more uniform over the life of the powder, with no loss over time as with powders stored in varying temps. (Which I used to do)