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Sun glare: A real concern for motorists

From the National Weather Service

From the National Weather Service

Being on the road in the morning and the afternoon can already be a challenge because of traffic, but now there’s another thing for Oklahoma drivers to worry about this time of year: The glare from the Sun.

We see a variety of weather over the southern Plains during the year. We have become accustomed to large hail, tornadoes, blinding snow storms, flash flooding, and deadly heat. But there is another subtle, yet very significant risk that we face during this time of year; the glare of the sun as we drive our vehicles.

The sun spends roughly an equal amount of time above and below the horizon. The rising sun aligns itself perfectly with our many east-west roadways, including busy freeways such as Interstate 40. It is during the first 15 to 45 minutes of sunrise that sunglare is worst and a serious hazard to motorists.
Sunglare-Graphic

There are only two times of the year when the Earth’s axis is tilted neither toward nor away from the sun, resulting in a “nearly” equal amount of daylight and darkness at all latitudes.

These events are referred to as Equinoxes and occurred twice a year. The Autumnal equinox was September 22nd at 3:44 pm (the first day of fall).

At the equator, the sun is directly overhead at noon on these two equinoxes. The “nearly” equal hours of day and night is due to refraction of sunlight or a bending of the light’s rays that causes the sun to appear above the horizon when the actual position of the sun is below the horizon.

Additionally, the days become a little longer at the higher latitudes (those at a distance from the equator) because it takes the sun longer to rise and set.

Therefore, on the equinox and for several days before and after the equinox, the length of day will range from about 12 hours and six and one-half minutes at the equator, to 12 hours and 8 minutes at 30 degrees latitude, to 12 hours and 16 minutes at 60 degrees latitude.