Yes, a battery grip can help in cold weather, but mostly because it lets you carry more power without opening the camera as often. Cold reduces battery performance, so the most useful strategy is usually to keep spare batteries warm in an inside pocket and rotate them as needed.

Using two batteries in a grip can extend shooting time before a swap, but it won’t stop cold from reducing capacity. A single battery in the camera body may stay slightly warmer than one in the grip, since it’s closer to the camera’s heat and your hand, though the difference is usually modest.

If your grip accepts AA batteries, disposable lithium AAs are a strong option for extreme cold and are known to work well at very low temperatures. Some users also report good results from lithium iron phosphate cells in compatible grips.

Best practical approach: use the grip if you want longer runtime and fewer battery-door openings in snow, wind, or ice, but still carry warmed spares in a pocket. For the cheapest reliable setup, keep rotating warm spares; for the best extreme-cold AA option, use lithium AAs if your grip supports them.