I'd think that in general, cold resistance of any sort would protect you completely from normal extremes of cold. I don't know if this is in the RAW or not, but it seems obvious. As Cheiromancer point out, damage per minute is much less than damage per round.
The question is, at what point is damage per minute enough to overcome energy resistance? Suppose you only have cold energy resistance 1, and you are out in -20 degree weather? This is up to 10 damage per minute, is this enough to occasionally discomfort you? One way would be to assume that since there are 10 rounds in a minute, that your Energy Resistance to damage per minute is 10 times that of your resistance to damage per round. This means that a character with cold resistance 1, reduces the ammount of damage from normal cold by 10 per minute, which is easily enough to stay out in -20 degree weather as long as you like.
At some point, its -70 below and the wind is howling at 50 mph, cold resistance 5 might not cut it, but the RAW say nothing about that either.