The operating temperatures of lithium ion batteries are there for your safety and probably include a margin. You’ll likely find them listed in the manual. They also have different tolerances for temperature while, charging, idle storage, or discharging. With that said, exceed them at your own risk. If I was in your situation, I personally would look for a bike with a removable battery that I can charge indoors. This way you also won’t have to deal with the performance hit that comes from cold weather operation. If you are dead set on a bike with an integrated battery, I own one and I bring it in from the garage during cold spells. No risk of overheating where I am. It’s inconvenient having my bike sitting in my office/bedroom, but if it’s just a few weeks out of the year, I can live with it.