According to the Rad website: The components are all water resistant and work very well in wet conditions, but you should take care to keep your bike parked indoors whenever possible and in a dry location when in storage. The display, motor, battery pack, and throttle are all designed to operate just fine in heavy rain, normal drizzle, or a soggy wet morning commute in Seattle, but you should always take care to dry off your bike and store it properly between use to prevent corrosion. I take that to mean no protection is needed, but a shower cap or a plastic bag should work fine.
TT