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Summer Sunbeams and Crepuscular Rays

Summer can bring a season of spectacular rays of sunlight thanks to pop-up storms and towering cumulus clouds
Credit: Terry Kelley

LOUISVILLE, Ky. — I want to show you a dazzling display of sun rays.  Some of the pictures below are sunbeams (rays of sunlight during the day) and crepuscular rays (rays of sunlight and shade once the sun goes down below the horizon). 

Let's start with crepuscular rays.  The pictures below were taken recently right around sunset.  This time of year we often get pop-up late afternoon and evening showers and storms.  These towering cumulus clouds can block some of the sunlight, creating a ray of shade across sky, cutting through the regular sunlit sky. 

This first image shows a cumulus cloud on the right side of the horizon blocking the sunlight, and casting a large ray of shade across our sky.  This is a true crepuscular ray because the sun is below the horizon.  The word crepuscular refers to basically anything relating to twilight.  Some animals are called "crepuscular animals", because they are active around sunset.

Credit: Terry Kelley
Credit: Sonja Radojevic
Credit: Sherry Mathers
Credit: Don Yeoman Jr.

The rays seem to come together or converge on the horizon.  This is a visual illusion, as the rays are actually parallel lines.  It's just like a road that appears to converge on the horizon in the distance. 

The images below show rays that could technically still be sunbeams, but to me, the sun is close enough to the horizon to be producing crepuscular rays.  

Credit: Terry Kelley
Credit: Anthony Popplewell

The next pictures below show some nice sunbeams.  The bright rays are "normal" sunlight.  The sun rays are seen by reflecting off particles in the sky.  The darker, shaded areas are caused by the sunlight blocked by the cumulus clouds.  So, less of the sunlight is being reflected by particles in the sky.

Credit: Alyssa Rowe
Credit: Stephanie Sauer
Credit: Deana Smith Andrew

The next picture shows the towering cumulus clouds that block the sun's rays.  During the summer, there is often very little wind in the upper levels of the atmosphere.  So, the clouds grow straight up, and can be tall and skinny - helping to produce the sunbeams and crepuscular rays!

Credit: Rebecca Marks