I agree the c-rating is too low. the temperature outside can affect performance but the cells are probably warm from your house and probably warmer when your done because of the low c rating so its not much of a factor in this case.
I have a similar setup(old low c lipos, novak 6.5hv, xray xb8) and have been playing in -10 degrees C. 4200mah pack cuts out at 3000 mah. I have the 4.5 motor and it is balistic but this pack can't handle it. my gearing is a bit lower but should work out to the same as your as I'm running in high drag snow.
Current active RC's; Brushless Xray XB8, CRC Pro10, Tamiya M03, Xray M18, Losi Micro-T. Inactive list; Losi XXX-S, Duratrax Evader st, Traxxas TRX-1, Traxxas E-maxx, Brushless Ofna 9.5, Corally sp12m