Softball is an outdoor sport, predominantly played in the spring, which in most places means at least occasional cold weather. Bats made of some materials become less useful in the cold weather, while the performance of bats made with alternate materials is largely unaffected. Cold weather increases the risk of damage in all three kinds of bats.
Softballs -- which are actually harder than baseballs -- harden further when exposed to low temperatures. The added density of the ball puts more stress on the bat during a swing, making bats of all materials more susceptible to damage. Aluminum bats, claims the Atlantic Softball Club, have an impaired performance in cold weather. Wooden and composite bats do not have this problem.
Temperature variations can make softball bats of all materials vulnerable to damage. Some, like aluminum bats, become more vulnerable to dents. Composite and aluminum bats can shatter or simply break in two. Composite bats can safely handle this added stress down to 60 degrees. Aluminum bats tend to fare better, with a safe usage limit of 50 degrees.