I've tested Big Game in several cartridges at zero degrees Fahrenheit, several times since it appeared over 15 years ago.
Generally, if the velocity is within about 30 fps at zero of the same load's velocity at 70 degrees, I consider a powder cold-resistant, partly because a string shot with the same load will often chronograph 30 fps different on the same day. Big Game has qualified easily.
Am planning to run some warm-weather tests as soon as the temperatures become consistently warmer in a month or so--but so far during routine testing in temps up to 85+ haven't seen anything unusual from it--which can't be said of all spherical powders.
