Since you live in Idaho, and I live in Montana, we will both have similar issues with o-rings in cold weather. The weather in both our locations can be colder than Buna rubber o-rings were designed to handle, and I have had issues with cold weather induced air leaks. Never had an issue yet in hot weather except for a worn out o-ring on the pellet probe. You might want to review what I just posted under the Thread "BSA Lonestar .25 leaky valve fix" and see if it might apply to you. This can happen even with a new rifle in extreme cold weather colder that what Buna o-rings were designed to handle. From what I found on the internet, Buna o-rings are good down to about -10F, but the weather here lately has been colder than that, and my Lonestar developed a cold related leak just like it did last year.
However, my issue did not come up until my rifle was several years old. And remember, PCP air rifles will need the o-rings to be oiled on a regular basis unless you want air leaks to develop. Many PCP owners do not perform this routine maintenance, and your rifle may have shipped with dry o-rings and/or had a long cold soak in transit to your location.
Phil