Wind affects our bodies, but wind chill is a non-issue for batteries. Remote batteries inside our presumably warm cloths work well, but require a little personal intervention to create the remote battery box, cord, and camera component for most brands.
A small insulated case and hand warmer can be very helpful as well. I have a manufacturer remote set for Nikon, but having switched to Canon years ago, it doesn’t help much now. If the voltages are right, I suppose one could use the “wrong” brand battery case and cord along with a cobbled together camera component, but it’s easier to just carry extra batteries.

This is probably a well-known phenomenon and a well discussed topic, but it’s interesting to me since I just observed it firsthand. I went on a photo shoot on a very cold day in Chicago…..shooting from a breezy high-rise roof top which made it even colder. I started with a fully charged battery in my Fuji X-T2. As I shot multiple exposures, I notice the battery (charge) indicator declined rapidly and went red, indicating complete exhaustion. (At first, I couldn’t believe what was happening because the decline was so fast). I switched to a (warm) battery from my pocket and put it in my (now) colder camera. After a few minutes and a few exposures, the same thing started to happen. I ended the session with about half the shots I usually get from the batteries….(and my freezing hands). So, my observation and conclusion…battery life declines rapidly, as much as 50% in very cold weather. The exposures appeared mostly normal since I stopped shooting before the battery indicator went red. And yes, these are rather new, Mfg labeled batteries. My new practice for cold weather shooting---carry multiple batteries in warm pockets and expect to change them😊 Any quick thoughts would be appreciated…thanks

The Fujifilm X-T2 is a battery hog overall, even when the temps are warm compared to a lot of other cameras. I have the X-T2 and have noticed the same decline of battery charge these past few days in Connecticut with temps in the mid 20s. I just ordered a used vertical power booster grip from mpb. The price was right compared to new.
Question: I keep a couple of charged batteries in my camera bag as backups. I'm assuming they will be affected by the cold weather just sitting in the bag. How does this affect the discharging/charging life span of the battery? If the back up batteries in my camera bag weren't used during the day of shooting do I need to put them in the charger to 'top them off?'

This is probably a well-known phenomenon and a well discussed topic, but it’s interesting to me since I just observed it firsthand. I went on a photo shoot on a very cold day in Chicago…..shooting from a breezy high-rise roof top which made it even colder. I started with a fully charged battery in my Fuji X-T2. As I shot multiple exposures, I notice the battery (charge) indicator declined rapidly and went red, indicating complete exhaustion. (At first, I couldn’t believe what was happening because the decline was so fast). I switched to a (warm) battery from my pocket and put it in my (now) colder camera. After a few minutes and a few exposures, the same thing started to happen. I ended the session with about half the shots I usually get from the batteries….(and my freezing hands). So, my observation and conclusion…battery life declines rapidly, as much as 50% in very cold weather. The exposures appeared mostly normal since I stopped shooting before the battery indicator went red. And yes, these are rather new, Mfg labeled batteries. My new practice for cold weather shooting---carry multiple batteries in warm pockets and expect to change them😊 Any quick thoughts would be appreciated…thanks