Yes and no, for several reasons.
1. Water conducts electricity only if it has dissolved ions (e.g. salts) in it. Tap water has some, sea water has more, but rain water has very little, unless it is mixed with sweat from your skin.
2. Lightning is a spark, a channel of plasma that is formed as the voltage separation of the thundercloud overcomes the electrical resistance of air. Lightning doesn't really care what it hits as far as the amount of electricity delivered is concerned because this plasma channel is a perfect conductor, and if anything else isn't a good enough conductor, the lightning will ionize it too.
3. Almost anything is a better conductor than air. Once the lightning hits it and goes into standard electric current physics, there will be a huge current flowing through it, enough to neutralize the voltage separation of from clouds to the ground.
Basically, being a poor conductor of electricity can make you less likely to get hit by lightning, but the amount of energy and the amount of electricity delivered isn't going to matter much.