Actually a rainbow around the sun is a perfectly normal natural phenomenon.
Also known as a 22 degree halo or a sun halo, the ring is caused by sunlight passing through ice crystals in cirrus clouds within the Earth's atmosphere. The crystals bend direct sunlight, projecting it elsewhere into the sky, and at a certain angle -- you guessed it, 22 degrees -- a halo can be seen around the sun. It happens most often in the northern hemisphere in the fall, winter, and spring when the jetstream takes a bend towards the south, chilling the upper atmosphere.
In weather lore, it means that rain is likely.
In Judeo/Christian belief, the rainbow is a reminder of the Biblical covenant that Yahweh will not send another flood upon the earth.
Some Newage pundits claim that a rainbow around the sun portends a period of great change.
So you have your pick of meanings. Personally I'd go with the idea that it is a sign of rain to come as ice crystals in the upper atmosphere often end up creating rain clouds and subsequent rain.