How much is runtime impacted by cold weather?

This comes down to two things: the type of battery chemistry used, and how warm you can keep the battery during operation.

For the batteries, we use Li-Ion cells from LG and Samsung, just like basically all of our competitors, so there is no alien technology nor significant difference in how they respond to cold, as they all increase internal resistance and thus reduce capacity the colder they get. As a general rule of thumb, these cells according to the manufacturer spec sheets see roughly a ~20% reduction in capacity at 14° F and another 20% below zero, if all else is equal.

One of the main differences in our light design, is that our battery cells are placed in intimate contact with the LED heatsink, so that waste heat from the LEDs actually serves to keep the cells slightly warmer than external temperature, which means the impact of cold weather is not as severe as most of our competitors. That's not to say there is no impact, but the impact is not as bad.