Although my personal policy is to ride rain or shine, I don't like to take other folks out when it's above a 50-60% chance (depending on the rate of rainfall) and some other factors. The other leaders and I haven't posted the rule so that we can watch the radar and make a judgement call for each ride.

We typically have a very wide range of abilities ride with our A-C groups, and wet roads can throw enough of a wrench in the works, that we try and avoid the hassle of someone going down.