Does weather affect the battery?

Yes. Although the battery is fully protected inside the frame, temperature can affect the battery.  

You can certainly ride your BZEN in the winter but please note that below zero degrees Celsius, as it is the case for all batteries, the performance of the battery is reduced. Therefore, the bike should ideally be stored above 0 degree Celsius, insofar possible. Above all, it is important to avoid charging the bike in sub-zero temperatures

Higher, summer temperatures can affect the performance of the battery as well. We suggest not to store the bike in full sun. Like all modern electronic equipment our batteries are protected from overheating by internal thermal sensors, but a good rule of thumb is not to let expose batteries to extreme heat.