You might have noticed something eerie in the night sky lately. Reports of mysterious green glows above American cities have been popping up across social media and local news outlets. These otherworldly phenomena have sparked curiosity, concern, and countless theories about what might be causing them.
From spectacular aurora displays reaching unusually far south to intense thunderstorms creating supernatural-looking skies, several fascinating atmospheric processes could be behind these green glows. While some explanations are more common than others, the truth is that multiple natural and scientific phenomena can paint the sky in shades of emerald and jade.
Aurora Activity Pushing Southward
The northern lights illuminate the night sky over a camper’s tent north of San Francisco in Middletown, California on May 11, 2024. This remarkable sighting shows how auroras can appear much farther south than their typical polar territories. The green we see in the aurora is characteristic of oxygen, while hints of purple, blue or pink are caused by nitrogen.
The Northern Lights, or aurora borealis, can sometimes appear in unexpected places due to a combination of solar activity and Earth’s magnetic field dynamics. Different gases and altitudes produce different colors: Green: Oxygen, about 60 miles (100 kilometers) Red: Oxygen, higher than 150 miles (generally 180 to 250 miles (300 to 400 km). When solar storms intensify, these natural light shows can extend their reach into regions where people rarely expect to see them.
Solar Storm Intensification Effects
Solar Wind and Charged Particles: The sun constantly emits a stream of charged particles known as the solar wind. These particles are primarily electrons and protons. During periods of intense solar activity, such as solar flares and Solar Flares and Coronal Mass Ejections (CMEs), the number of charged particles released increases significantly.
These heightened solar events create the perfect conditions for auroras to stretch far beyond their normal boundaries. The primary drivers – solar activity and Earth’s magnetic field – are influenced by factors beyond climate change. However, climate change can indirectly affect the Northern Lights by altering atmospheric and geomagnetic conditions. The result can be stunning green displays visible from places like Texas, Virginia, and even southern California during particularly active solar periods.
Thunderstorm Green Sky Phenomenon
The occasional greening of the sky during large strong thunderstorms is a well-known phenomenon, at least to severe weather enthusiasts, and can gain some notoriety once in a while. In early July 2022, for example, a derecho that moved roughly from Montana through South Dakota and into Iowa produced a flood of green sky photos on social media and news sites, as well as articles attempting to explain the phenomenon.
Now you may remember from school that blue and yellow together make the color green. The same applies to a green sky from a thunderstorm. Late in the day, the sun is low in the sky, and the color is yellow to orange. So when the yellow light from the late-day sun hits the blue light scattered by a thunderstorm that contains a lot of ice, you get green. It takes an incredibly high amount of water and ice to create these colors. So a green sky is a visual signal that the storm approaching is incredibly intense.
Water Droplet Light Scattering
Researchers remain undecided about the exact mechanisms that cause the sky to appear green in certain thunderstorms, but most point to the liquid water content in the air. The moisture particles are so small that they can bend the light and alter its appearance to the observer. These water droplets absorb red light, making the scattered light appear blue. If this blue scattered light is set against an environment heavy in red light – during sunset for instance – and a dark gray thunderstorm cloud, the net effect can make the sky appear faintly green.
Research from the University of Wisconsin-Madison has shown that storms with the most intense green coloration typically contain the largest concentrations of suspended water and ice. The physics behind this phenomenon involves complex interactions between light wavelengths and microscopic particles suspended in the atmosphere. When conditions align perfectly, even urban areas can experience these dramatic color transformations.
Urban Light Pollution Interference
ALAN (Artificial Light At Night) referrs to the excessive and misplaced artificial lighting emitted in our cities at night. This lighting can brighten the night sky so much that it becomes difficult to see stars and other celestial bodies, such as the Northern Lights. In urban areas, light pollution can be so intense that it can make the night sky up to 100 times brighter than in a natural, unlit location. This means that the delicate light of the Northern Lights is often drown out by the glow of city lights.
However, when natural green glows are intense enough, they can sometimes overcome even significant urban light pollution. This creates a particularly striking contrast and makes the phenomenon even more noticeable to city dwellers who aren’t accustomed to seeing natural light displays in their metropolitan environments.
Atmospheric Sprites and Green Ghosts
Green ghosts – blurs of light that sometimes follow lightning – get their color from oxygen and metals in space dust. These include vibrant red lights called sprites, which are sometimes followed by eerie green ghosts. After a sprite, a subtle greenish gleam – a ghost – sometimes appears near the sprite’s top. Sprite hunters noticed such glimmers of green in videos they had taken since 2019.
These upper-atmosphere phenomena occur at much higher altitudes than typical thunderstorms, creating unique green displays that can be visible across wide geographic areas. And now, scientists have unveiled exactly what is behind ghosts’ green hue. To create sprites and ghosts, you need a massive thunderstorm that holds a lot of electrical charge. Though rare, these events might explain some of the mysterious green glows reported over cities during severe weather events.
Supercell and Derecho Storm Effects
The late afternoon or early evening sun, sitting low on the horizon, provides the reddish light that, when filtered through thick storm clouds loaded with moisture, can combine with blue light from the sky to create a green hue. This effect is particularly strong in the presence of supercell thunderstorms, which are the main culprits behind tornado formation in the United States.
Common producers of these events include severe thunderstorms and derechos. A derecho is a cluster of storms that produces destructive wind gusts and hail for hundreds of miles and has the potential to impact millions of people. A July 2022 derecho event that moved through the Northern Plains produced hail, damaging winds and an eerie shade of green in the sky. These massive weather systems can create green skies visible for hundreds of miles, making them particularly noticeable in urban areas.
Regional Weather Pattern Shifts
Oklahoma and Kansas are known to experience green sky phenomena during severe weather events, though specific frequency data is not systematically tracked. However, climate patterns are shifting these hotspots, with increased green sky reports now documented in areas like Tennessee, Alabama, and even parts of the Mid-Atlantic states. The expanding range of these phenomena reflects broader changes in severe weather patterns across the continent.
This geographical expansion means that cities previously unfamiliar with green sky phenomena are now experiencing them more frequently. Urban areas in the Southeast and Mid-Atlantic regions are reporting green glows that their residents have never witnessed before, contributing to the sense of mystery surrounding these events.
Ocean Bioluminescence Events
“The sea from horizon to horizon in all directions took on a phosphorescence glow … the moon had just set and the whole sea was several shades lighter than the sky,” wrote J. Brunskill, an officer aboard a ship called the SS Ixion that had sailed through the Arabian Sea in 1967. Nearly 10 years later, another crew aboard a vessel named the MV Westmorland experienced a similar event in the Arabian Sea as it sailed through a “large area of bioluminescence,” according to the ship’s captain, P. W. Price. “The sea … glared a brilliant and bright green.”
While scientists do not know exactly why this rare glow occurs, it is likely a byproduct of high concentrations of microscopic bioluminescent bacteria called Vibrio harveyi, according to the study. This hypothesis is based on a 1985 chance encounter by a research vessel that had collected and tested a water sample during a “milky sea” event. Though these “milky seas” typically occur far from shore, coastal cities might occasionally witness reflections or distant glows from these extraordinary marine events.
The mysterious green glows appearing over U.S. cities result from a fascinating array of natural phenomena, each with its own scientific explanation. From solar storms pushing auroras into unexpected territories to intense thunderstorms creating optical illusions in the sky, these events remind us that our atmosphere is constantly putting on spectacular shows.
While these green glows might seem otherworldly, they’re actually beautiful displays of physics in action. Understanding the science behind them helps us appreciate both the power of nature and the complex interactions happening above our heads every day. What do you think about these mysterious green phenomena? Have you witnessed any unusual sky colors in your area lately?
