'Sun dog' rising: Deep freeze brings rare weather phenomenon to the Midwest as residents brave the cold to snap stunning photos

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The deep freeze gripping the Midwest has one upside for fans of the rare solar phenomenon known as 'sun dogs', dazzling residents throughout the region.

As temperatures plunged as low as -42F in Park Rapids, Minnesota and -31F in Fargo, North Dakota, sun dogs were spotted throughout the upper Midwest on Tuesday and Wednesday. 

The National Weather Service describes the phenomenon as colored spots of light that appear on either side of the sun due to the refraction of light through ice crystals. 

This stunning example of sun dogs was captured by Tim Barry in the midwestern Plains at sunrise on Tuesday

In Lake Madison in North Dakota, Jeremy Lundgren spotted this prime example of sun dogs from his vehicle on Tuesday

Also near Lake Madison, resident Cody Welu spotted a stunning example of both sun dogs and halo on Tuesday morning

In Hospers, Iowa, resident Susan Budden snapped the photo above showing sun dogs on Tuesday 

They are located approximately 22 degrees either left, right, or both, from the sun, depending on where the ice crystals are present. 

The colors usually go from red closest to the sun, out to blue on the outside of the sundog. 

Sundogs are also known as mock suns or parhelia, which means 'with the sun'.

The National Weather Service (NWS) confirmed sightings of both sun dogs and "halos" in Sioux Falls, South Dakota, on Tuesday morning.

On Twitter, photos of the phenomenon also poured in from North Dakota, Iowa, 

The National Weather Service in Sioux Falls, South Dakota tweeted this example explaining the phenomenon

In Chicago's northwest suburbs, Vincent Godinez spotted an example of sun dogs from his car on Wednesday

The painfully cold weather system that put much of the Midwest into a historic deep freeze was expected to ease Thursday, though temperatures could still tumble to record lows in some places before the region begins to thaw out.

Disruptions caused by the cold will persist, too, including power outages and canceled flights and trains. 

Crews in Detroit will need days to repair water mains that burst Wednesday, and other pipes can still burst in persistent subzero temperatures.

Before the worst of the cold begins to lift, the National Weather Service said Chicago could hit lows early Thursday that break the city's record of minus 27 set on January 20, 1985.

WHAT IS A SUNDOG?

Sundogs or parhelia are seen over a snow-covered field in Duluth. Sundogs, also known as mock suns because of the bright spots at either side of the sun, appear when light from the sun near the horizon is refracted by ice crystals in the atmosphere

The sight of three suns in the sky is enough to make most of us rub our eyes in disbelief, but centuries ago, the strange sight was seen as a bad omen. 

The unusual spectacle is called a parhelion or a sundog.

It is the result of a natural phenomenon in which sunlight passes though snow crystals in a particular way when they are suspended in the air.

Sundogs are created when sunlight is refracted by large, hexagonal ice crystals, such as those in snowflakes. 

They typically appear as two coloured patches of light either side of the sun and though rare, can in theory be seen anywhere in the world in any season.

They are created by the refraction of light passing through flat, hexagonal ice crystals in high, cold clouds.

The crystals act like prisms so that as light passes through them, it is bent by exactly 22 degrees before reaching viewers' eyes to make the illusion.

If the crystals are more randomly located in clouds, a complete ring around the sun is visible, called a halo.

Pictured is the moon halo over the, Isle of Wight. The moon halo is formed by a high-altitude ice crystal cloud that gathers around the moon

But if the crystals sink through the air, they become arranged in vertical lines, so that the sunlight is refracted horizontally, to make sundogs, as seen in these images.

If the phenomenon is seen as the sun is rising, the sundogs gradually move further away from the sun, but always stay at the same elevation, so the three 'orbs' appear to be the same distance from the horizon.

They are reddest in colour when they are near to the sun and fade to yellow, orange and then blue as they move away. The colours of sundogs merge into a white halo in some instances.