The electro-chemical reaction is more favorable at higher temperatures. Consequently, when it is warmer, the batteries will perform better. This is also evident from practice: old batteries do not start the car when it's cold.
Now, about storing batteries. I heard some people store their batteries in the refrigerator. How, if at all, is it beneficial, as opposed to storing at room temperature? If it is not beneficial, what are the souses of such misconception?