LOUISVILLE, Ky. — Summer is fast approaching, and with it comes later sunsets, earlier sunrises and longer days overall.
Louisville’s first 9 p.m. sunset comes Friday, May 31st. Sunsets will continue to be after 9 p.m. until July 24th.
Though the 9 p.m. sunsets continue through July, the days will gradually get shorter after the summer solstice on June 20th.
Why do the days get longer?
Why do the days get longer? It has to do with Earth’s axis and tilt toward the sun during summer, and the sun angle and azimuth.
The sun angle, also known as the altitude angle, is the elevation of the sun’s position in the sky measured horizontally from the ground. Put another way, the sun angle at sunrise is 0°, while at 90° if directly overhead (which occurs at the equator during the fall and spring equinoxes). This means the sun is never truly “overhead” in Louisville.
This is different than the azimuth angle. The azimuth angle is the angle of the sun is the direction from which sunlight is shining from.
Here’s an example. The summer solstice is the longest day of the year. At solar noon on the summer solstice, the azimuth in Louisville is 180°, meaning the sunlight is coming from due south.
The sun angle (altitude angle), is roughly 75°, meaning if you looked at the horizon and drew a line from the sun to yourself, the measured angle is 75°.
Enjoy the longer days and warmer weather here in Kentuckiana!
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