I get this question a lot...........how cold is to cold to be swinging a shaved bat?  My recommendation is not below 65 degrees.  From all the years i have been playing ball, i have noticed i tend to break bats rather easy below this mark.   Composite bats flex at impact which is why the distance you see off a composite bat usually far exceeds an aluminum bat.  In the cold, the composite fibers harden causing the bat to stiffen at impact which can mean disaster for your shaved bat.  Also to consider are the balls.........have you noticed balls fly better at night?  The reason being is 2 fold, lower temps and humidity levels.  Most balls are very sensitive to temperature fluctuations and harden or loosen depending upon the conditions.  The stamped ball compression you see such as 44/375, 40/325, 52/300 as examples are AVERAGE compression and core measurements.  In the heat, balls loosen and go flat very quick, in the cold balls harden, they last longer and they travel much further.  Moral of the story is harder the ball, further it will travel, but the faster your bat will break.  

Is there anything i can do if the temperature is below 65?  In short, no.  I would suggest a stock bat is used in these conditions, however, even a stock bat can break prematurely in the cold.  What about bat warmers?  Well in theory the bat warmer will loosen the bat, but you still have a very hard ball to swing at.  What if it is 60?  Again, my suggestion is 65 based upon my experience, but 5 degrees is 5 degrees.  I do not suggest 60 for a reason.  

In conclusion, everyone is a little different.  Some can get away swinging bats in the cold, others cannot.  From a conservative stand point, i would keep it above 65.