To a certain extent I agree with Erebus. I am not sure whether I read his reply as he intended it, so I would hesitate before disagreeing with him on any detail.
So perhaps I may paraphrase (or rephrase, or give my own paraphrasis
)
St. Elmo's Fire is in itself totally harmless. It can be spectacular to watch. It is a sign of slow static discharge by the aircraft to atmosphere and therefore that the static wicks are working (fairly hard). The aicraft is accumulating static at a rate close to the rate at which it can shed it. This will not cause lightning strike.
It is, however, a portent of other problems. Provided the WXR is on, you should be able to see any storm cells in the vicinity and therefore avoid them. What is more difficult to see on radar, though, is volcanic ash or sandstorms, both of which can be accompanied by St. Elmo's Fire.