You don't need a weatherman to know which way the wind blows.
This phrase is famously used in Subterranean Homesick Blues by Bob Dylan. The metaphor itself is so simple and powerful I'm sure it would've been a proverb by now had we weather forecasts a couple of hundred years ago. Now imagine my surprise when I learned that Dylan apparently coined the phrase himself:
Most famously, its lyric "you don't need a weatherman to know which way the wind blows" was the inspiration for the name of the American radical left group the Weathermen, a breakaway from the Students for a Democratic Society. In a 2007 study of legal opinions and briefs that found Bob Dylan was quoted by judges and lawyer more than any other songwriter, "you don't need a weatherman..." was distinguished as the line most often cited.
Does this mean that there is no factual evidence of this phrase being used prior to the song, or did he just make an existing phrase (more) popular?
I'm not trying to belittle Dylan's influence—just plain curious how far it extends in this case.