This is pretty common, especially for Loti that are stored outside. The water sits in the "valley" of the cylinder head cover and eventually makes its way past the ignition coil seals. I've found that it's worst on cylinder 1 (closest to crank pulley). The area of greater concern is seeing hot spots (look like little brown dots) where spark is passing through the ignition coil body and grounding through the cylinder head. That's usually a sign it's about time to replace the coil packs.
Like most people, I coat the living sh1t out of my ignition coils with dielectric grease.
2005 Lotus Elise, naturally aspirated and always at redline!
2018 NASA Great Lakes Region TT4 Champion