The strongest display of aurora borealis, or Northern Lights, in 21 years was impacted over the weekend by heavy cloud cover in many locations, particularly Pennsylvania.

And much like the recent solar eclipse, those weather conditions generated disappointment in many hoping to witness a spectacle.

Some local residents expressed a sense of frustration in social media posts Saturday and Sunday. Comments reflected the exasperation.

“Unfortunately we were cloud covered here in Drums,” said Dorothy Allesch.

“I was looking when I was in Walmart parking lot last evening late, no luck,” said Brenda Parrish, Tamaqua.

Despite heavy cloud cover, it was still possible in some locations to catch a touch of the vibrant color by waiting for a break in the overcast.

Another method was to set a camera for long exposure. A camera lens is able to capture more than the human eye, producing an image more detailed and colorful than what was actually visible.

The colors were so vivid that they bled through the clouds.

Those who were lucky to have no cloud cover to deal with were able to capture strong pillars, or rays, of color.

The lights are the result of activity on the sun’s surface.

There, solar storms emit clouds of electrically charged particles which can collide with Earth, according to London’s Royal Observatory.

The result is a display of colors, typically strongest at the magnetic poles. This time, shades of purple and green appeared to be the strongest hues.

The display over the weekend was so strong that it was visible as far south as Florida.