Hi djtwok,
Thanks for using the Apple Support Communities. I understand that you are having some issues with the flash on your iPhone when it is cold out. I'm not sure how cold we are talking, but you may want to make sure that you are using your iPhone within the range outlined below:
Environmental Requirements
- Operating ambient temperature: 32° to 95° F (0° to 35° C)
- Nonoperating temperature: −4° to 113° F (−20° to 45° C)
- Relative humidity: 5% to 95% noncondensing
- Operating altitude: tested up to 10,000 feet (3000 m)
iPhone 8 - Technical Specifications - Apple
Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behavior to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures.
Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures - Apple Support
Regards.