Actually, all powders are temperature sensitive to some extent. A general rule of thumb is that ball powders are more sensitive than extruded powders.
Some of the effects of cold temperatures that you will notice are lower velocities, slow or hang fires etc. High temperatures will cause just the opposite and can lead to excessively high pressures, blown primers etc.
This is why its important to write down the temperature when you are testing a load. I always let my rifle and ammo adjust to the outside air temperature before I shoot at the range, so I can record accurate results for the conditions.
If you have a load that shoots good at say 70F and you notice it starts mis-behaving at 30F, a couple things can be done if you have to shoot at 30F or colder. I've put a hand warmer (the little disposable ones) in with my ammo and wrapped it in a jacket. If you are hunting, you can carry a couple shells in a pocket to keep it warmer, then load it just before you shoot.
On the flip side, too hot of temperatures can raise pressures significantly. Although I've never done it, I've seen guys keep loads in a cooler in the summertime, because if that ammo got hot, it would be too high pressure.
Hope some of that helps, I'm sure others will add a lot more detail.
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