Forget the transit of Venus coming Tuesday. Another celestial phenomenon Monday was causing residents of Tampa Bay to look to the sky before grabbing the camera.
The occurrence is a halo around the sun, or a 22-degree halo.
Also known as a nimbus, icebow or gloriole, it is an optical phenomenon produced by ice crystals creating colored or white arcs and spots in the sky. Many are near the sun or moon but others are elsewhere and even in the opposite part of the sky. They can also form around artificial lights in very cold weather when ice crystals called diamond dust are floating in the nearby air.
They are produced by the ice crystals in cirrus clouds high in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion. The crystals behave like prisms and mirrors; refracting and reflecting sunlight between their faces; sending shafts of light in particular directions.
The effect can occur as many as 100 days a year, according to an entry on the website Wikipedia.
Monday afternoon, Twitter feeds all around Tampa Bay lit up with photos of the halo, including one from WFTS meteorologist Denis Phillips, who explained on his Facebook page that, "… if the winds are from the SW, that often means rain is on the way within 24 to 36 hours."