as others have said cold is not the issue. what does become and issue is in the cooler weather with wind you wind up going through a ton of fuel and on a long smoke the ash eventually builds up enough to choke the fire. what i do is, take the middle section (WITH the lid) and move it to the side for a moment. the temp will start to lower in the chamber but not that fast. i put handles on my fire grate so i can pick up the fire grate and shake the ash out. i then set the fire grate aside (on something that will not burn!!!) and with a small garden trowel and metal fireplace ash bucket, i remove as much ash as i can. i then put the fire grate back in reload more fuel let it get some heat and going then just pop the entire middle section with lid back on top and let it regulate temp again. has been working well for me lately on LONG smokes.
you know how they say every piece of meat has it's own time. well i had an 8 lb butt take 19 hours recently. the other 8 lb butt took 12. thank god i cooked both. one was ready in time for dinner and the other was good for the fridge and left overs.