Re: NNG Tool Question.

Typically freezing (0C) is within the specs for the NiCd, NiMH, and Li chemistries used for batteries in tools. The nickel and lithium chemistries pretty much don't care, and actually prefer to be stored on the colder end of the spectrum. The electrolyte isn't going to freeze at 0C, and most are going to be rated down to -10C or -20C. More importantly is their state of charge when put in storage. NiMH and NiCd should be stored fully charged (but not stored on the charger...). Lithium chemistries should usually be drained down to 50% of their charge remaining and stored that way if you don't intend to use them for long periods of time. If stored fully charged, they lose overall capacity. If stored empty (or self discharge gets them to empty while stored), they can be permanently damaged.

Temperature has more an effect on the mechanical considerations of the electronics, like solder joints and electronics within the pack. The contraction of all the little bits inside can lead to broken solder joints and so on.

Personally I'd drain the lithiums to 50%, charge the nickels, and store them all in a cool spot in the house for the winter. Don't worry about bringing chargers, as none of these should self-discharge enough to be an issue.