I'm not sure of the "operating temp" of yeast, however I did run across a suggestion on a way to compensate this problem. This will also help reduce 'night spikes' of co2 concentration. What you do is set your homemade bottle(s) into a small bucket and fill that bucket with some water. Place an aquarium heater in the water and put it on a timer. If you have a timer for your lights, put it with them. That way it will heat it up during the day and encourage the yeast to get to work. And at night, it will cool down, especially in your basement, reducing an overload of co2!
Hope this helps!