Just like mobile phones, the batteries of the electric bike don't like extreme cold and heat. If the battery is put at extreme temperatures, its life expectancy would dramatically deteriorate and even it may result in a fire which poses a huge threat to people's lives and property.
Hence if you live in an area where the summer is too hot or the winter is too cold, it's advisable for you to store your bike in your home. Note that it's unnecessary for you to take the battery off the bike when you store it. Also, don't let the battery run out of charge completely and leave it in your storehouse for a long time, and don't leave your electric bike out in the heavy rain or snow.
As for the place to store the bike, it's ideal to put it on flat ground rather than putting it on rough land with uneven holes in case the bike falls and damages its components.