In my looking on BD inverse sensitivity, it appears that in very cold conditions the granules fracture, making them smaller and removing any coating on one side of the kernel, both of which contribute to a faster burn rate. It seems like the process is irreversible, so once the powder had been exposed to extreme cold, it would be a faster powder regardleess of temp. Might make a good experiment to put a few rounds in the freezer overnight, then chrono those that had never been frozen, those frozen and thawed, and those that were still cold.
I have read of many who never noticed a difference, some who got low pressures in the heat, and some who got high pressures in the cold. It seems like the temp sensitivity was below 0*f though, so not likly for many people to hit it.