Just like you, electric scooter batteries don't like cold and humidity. Store yours in a dry and heated location, ideally between 15°C - 30°C.
As a rule of thumb, the ideal battery charge level during storage is 75%. Do not let it drop below 20%, but also don't overcharge it as this can be very harmful. The sweet spot is between 75% and 85%.
Power your scooter on once a month to see if the charge level is holding up or dropping. If you notice that it's lower than what it was originally, charge it up to the 75% - 85% level once again before putting it back.
Riding in the snow or rain can allow humidity to enter the case of your scooter, corroding the electrical parts. We know it might be hard to part with your best friend for the season, but it's best to avoid exposing it to wet conditions and/or salt.
Though most scooters come with a battery management system which includes overcharging protection, it is damaging to the battery cells to overcharge them for extended periods of time. None of us will unplug our scooter the second it's charged, but we can all try to minimize the amount of time it's overcharging for.
Last but not least it's important to keep your bearings greased up! You should use grease-based lubricant such as Jig-A-Loo (orange bottle) to spray over your wheel bearing while the wheel is being turned. Afterwards, wipe off excess lubricant with a paper towel. This process is shown in this clip: