Did alot of reaserch on the effect of cold hope you can use the info.
Video links 3 part serries
http://www.youtube.com/watch?v=NMu0tqfpXe8
http://www.youtube.com/watch?v=gr_rP_6rt18
http://www.youtube.com/watch?v=765hmKWUy-8
Here is the readers Digest version in print for the none video crowd
Cold Effects on PCP
What we learned form our test is that on average you will loose 20 FPS in velocity when going from 70 deg. F to 30 deg. F
You will loose an average of 425 PSI when going from 70 deg. F to 30 deg. F
PSI per shot does not change nor does shot count unless you do not top off you rifle after it cools down to ambient air temp.
Lost shots from not toping off was 13 shots Air Ranger, 17shots FX500, and 9 shots Huntsman. Quite a substantial impact on a rifle with a 24-30 or so shot count to loose 10 shots on average.
Test Rifles were
(FX is Regulated)
500cc Air Ranger .25 500cc FX500 Royal .25 114cc Huntsman Classic .22
3300 psi fill 3300 psi fill 3000 psi fill
2800 at 28deg.F 2800 at 28deg.F 2650 at 28deg.F
500PSI lose at 28deg,F 500 PSI lose at 28deg.F 350PSI lose at 28deg. F
Hi 70 deg. F 989 FPS 881 FPS 890 FPS
HI 25 deg. F 964 FPS 859 FPS 870 FPS
loss FPS = 25 FPS 22 FPS 20 FPS
Far as accuracy You will have to decide . For me a 20 FPS at 20-50 yards has little effect on my point of impact.