I did an ebike front motor conversion on my hybrid. The controller is mounted high on the seatpost so my body shields it pretty well and it has rubber gaskets and seals around the wires. The various cables are a universal fit, were all too long and would have been messy, so I added a 4X4 covered plastic junction box just below the seat and tucked all the plugs and excess wire int to. It protects the connections from the elements and cleans up the bike. I use a set of snap-on fenders when the trails are wet - mostly to keep me, not the electrics, dry! The handlebar display and brake levers with cutout switches seem adequately sealed.

Like others I have been caught in the rain, and this time of year the trails have lots of water from snow melt, but I have never had any issues. In fact, the trails are so messy right now I have had to hose the bike off the last two rides. There is also a lot of grit from winter road sanding, so I use a no-residue silicone lube on the drive train, and re-lube often.

So - no issues so far. I have only had to ride a couple of miles in the rain, so I can't vouch for what would happen riding 25 miles in a downpour, but I don't anticipate any problems.