Tldr:

Do not store or charge battery packs in locations where the temperature is less than 50°F or more than 100°F

But it also says

The lithium-ion battery pack can be used in temperatures down to –4°F. Put the battery pack on a tool and use the tool in a light duty application. After about a minute, the pack will warm up and begin operating normally.

And

A cold battery pack may be placed directly onto the charger port but charging will not begin until the battery temperature warms to within acceptable temperature range. When a cold battery pack is placed on the charger, the charger may indicate the pack is not ready to charge. Please refer to charger operator’s manual. When the battery pack warms to approximately room temperature the charger will automatically begin charging