During a remodeling project two year ago, I moved unopened containers of powder (e.g. Varget, Bullseye, RL 17) to a cabinet in my garage --- and then forgot they were out there. These containers now have gone through two blazing hot Texas summers, as well as a couple of winters with reasonably cold periods. Do any of you have information as to whether temperature shifts between 20 degrees Farenheit and 105 degrees Farenheit degrade powder to the point where I should discard it?

99% of the powders out there are made for the military and designed to withstand severe temperature changes.
Check your powders by a Sniff-test. If they smell like solvent their O.k. If they have an acrid smell, and I mean curl your nose hairs they have gone bad. The powder grains will have changed color and look really strange as well.

Thanks for the excellent information, Rapidrob. I

I lived in Texas most of my life and stored powder as you describe..I now live in Idaho and we get many below 0 temps..I still have never had a problem..Go ahead and shoot the powder you have, you won't have a problem, same with ammo...This problem is over stated by experts trying to prove their existence IMO... Most of todays powder is stable as can be..Most of us use the same ammo year around and its more stable in your powder room than in the field..I load and store in the summer and its hot in my shop, I hunt in some terrible weather and never a failure in my many years of hunting and reloading...I have ammo I loaded 10 years ago and it still shoots in summer and winter..Old aged powder will be a reddish color, but may still work as a matter of fact but I wouldn't..Ive struck a match to a lot of old powder and it burned instantly..As a matter of fact Ive never know a round to misfire because of the powder, only the primer ignition as best I recall..I have heard all the horror stories, but are they legit? or misinterpreted????

I presently have 40 pounds of old WW2 4831 that has to be very old. I bought it in 1981 and it was old then. Its been in my shop ever since both hot and cold with extremes way beyond what Texas can produce I suspect...I use it for the .270 on ocassiona and its still as good as new..