Not exactly something you would forget, these phenomena are breathtaking and rare.

1. Fire Whirls

Video here.

These flaming vortexes can burn up to 2,000 degrees Fahrenheit, can create winds that surpass 100 miles per hour, can hurl out burning debris and can ignite everything in its path. No, these "tornadoes" are not actually created by the devil himself. In reality, they form when winds from a wildfire create a vortex. Then, combustible gasses from burning vegetation are sucked in and subsequently ignited. To see the full potential of these fire whirls, skip to about 2:40. For a manmade (though no less fantastic) example, check out the Slow Mo Guys and their fire tornado here.

2. Mammatus Clouds

Video here and here.

There are many theories as to how these clouds form, and it's part of what makes them so ominous. The other part, besides them looking like the sky is about to descend down upon us, is that they are indicators of severe weather. Occurring before, during or after thunderstorms and tornadoes, these haunting cloud formations remain stationary in the sky for up to hours at a time. Not only are aviators cautioned to stay away but us on the ground should as well!

3. St. Elmo's Fire

Video here and here.

This weather phenomenon is similar but not the same as lightning and ball lightning. The blue or violet glow is created when there is a concentration of electric fields like during a thunderstorm. It was named after St. Erasmo, the patron saint of sailors, because it sometimes appeared at sea during thunderstorms. Often, it is accompanied by a hissing or buzzing sound. In fact, it's very similar to a plasma globe.

4. Ball Lightning

"Fig. 2. - The globes of fire in the room."

Video here.

This extremely rare phenomenon has been widely speculated over for centuries. It wasn't until the 1960s that scientists even acknowledged that it existed. Now, they're just scrambling to figure out what it is. Most commonly associated with thunderstorms, these bright spheres vary is size, duration, and activity. Many eyewitnesses report smelling sulfur when one disappears. Many report that they disappear silently while others report loud, even explosive, ends to these balls of lightning. However, people do consistently report that they occur with other lightning strikes, they are generally spherical, they travel, and their brightness corresponds to that of a 60 watt bulb.

5. Asperatus Clouds

Video here.

Though they may look dark and gloomy, they usually don't produce any severe weather. Additionally, as you can see, they look like an ocean in the sky. It's as though you're looking at the surface of the water from the bottom of the ocean. As beautiful as they are, these clouds are actually quite a mystery to meteorologists everywhere. However, the Cloud Appreciation Society is petitioning for these Asperatus clouds to get their very own spot in the next edition of the International Cloud Atlas. Here you can see a more scientific explanation of this new classification of cloud.

6. Fire Rainbow

Video here.

Fire rainbows, ice halos, or circumhorizontal arcs (its scientific name) are sort of like horizontal rainbows in the sky. They are formed by ice crystals in cirrus or cirrostratus clouds high in the sky. The crystals reflect light like a prism to create a spectrum of colors suspended in the atmosphere. They are very rare but very beautiful.

7. Volcanic Lightning

Video here.

Though volcanic lightning or dirty thunderstorms aren't as rare as ball lightning, they are extremely cool looking. Similar to thunderstorms, ash, rock, and ice collide in a volcanic eruption. This creates enough static electricity to form the discharges that we see as lightning.

8. Lenticular Clouds

Video here.

These are the UFO clouds. Typically forming over mountains, moist air is caught on the top of waves of air currents. If the temperature is low enough, the moisture freezes and creates these stationary, lens-shaped clouds. Similarly, clouds can form on the top of each successive wave of air, creating a more commonly known phenomenon called a wave cloud.

9. Light Pillars

Video here.

Though light pillars look similar to the Northern Lights, they are a phenomena all their own. Similar to circumhorizontal arcs, these pillars are formed by light that has reflected off of ice crystals in the air. These hexagonal crystals fall through the air horizontally, creating a sort of mirror that reflects the light source. This optical illusion is typically seen in colder temperatures and has been misinterpreted as a UFO on many occasions.

These nine phenomena are all quite rare but fascinatingly beautiful. Some are more well known than others. Some are more mysterious than others. And some, like ball lightning, prove how strange and intriguing our world is.