Hey Dan! Well, first of all,
Heavy Rain is an awesome video game for the PlayStation 3... So if you're ever stuck inside due to the weather (and concern for your new ebike), you might enjoy checking it out
On to the real question! Personal safety is the biggest concern, especially if full sized cars are sliding around. Even if your ebike does fine with the water, it won't hold up very well to a big fall or collision with an automobile. Each electric bike is designed differently so I'm going to comment on the Volton Alation specifically. The battery pack is sealed pretty well with the new rubberized cover. I think that will be fine and prevent any water from leaking in. The motor should hold up alright as it is pretty much sealed and the wires are all covered and bound together. Keep an eye on them over time however because the action of steering may pull and twist the cables which could wear through them and start to let water in. You may want to trace the length of the cables and tape over vulnerable spots (but this could also trap water inside, so be thorough and check regularly).
The LCD and twist throttle are the biggest vulnerabilities in my opinion. I owned an ebike that had a similar display and the buttons got unresponsive after a couple of very wet rides I took. Had to replace it at a local ebike shop and that made me think twice the next time it rained. I started using a ziploc bag to cover the display whenever it rained. Any sort of basic protection will work and you may be able to do something similar with the twist throttle but be careful there because you wouldn't want to compromise your grip. Twist throttles are easy to replace and inexpensive, they tend to go out after a lot of use regardless of water. Try to avoid letting it spring back quickly when you are reducing speed, this jars the wires... and has cost me a couple of throttles over the years.
Great thinking in general about the rain, nothing lasts forever but water and electronics are always tricky. Thankfully, the
Volton ebikes use a modular design that lasts well and their support is good so you can get replacements as needed. As for the rest of the bike, try to dry it off and remember to lube the chain every few months (there are howto videos on YouTube that explain putting oil on and then wiping it and the dirt off). I recommend checking out one of the environmentally friendly lubes like these and the video actually includes some good tips about maintenance and cleaning from the owner of
Blue Monkey Bicycles ebike shop in Salt Lake City, Utah.