Friday is the last blue moon until 2018

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Blue Moon: Thrill This Week for Skywatchers Who Love The Moon

WEATHER.COM -- It's almost time for another blue moon, but we're not talking about a drink. In most cases, the term describes the phenomenon that takes place when there are two full moons in the same calendar month. According to Earth Sky, the next blue moon will occur on July 31.

Generally, the moon is only full about once every 30 days. This means the blue moon phenomenon can only take place if there is a full moon in the first few days of a month. The last full moon was on July 2.

The phenomenon occurs once every two or three years. The last one took place on Aug. 31, 2012. After this month, there won't be another Blue Moon until 2018, according to the Orlando Sentinel.

(MORE: NASA Releases Mesmerizing Video of the Moon's Phases)

The Other Blue Moon

The term blue moon has been a point of contingency for many years and has developed quite a few definitions throughout time. Earth Sky claims that the Maine Farmer's Almanac defines the blue moon as the third full moon out of four in a season. If there are usually three full moons in summer, spring, winter or fall season, then a blue moon would describe the third moon in a rare month that had four.

The concept of a seasonal Blue Moon may have been around longer than the modern definition, but the fight continues as to which definition is more accurate. Either way, your odds of seeing a moon that is actually blue in color are far less likely. These are entirely unpredictable and are based on conditions in the sky among other factors. NASA points to the year 1883 when Indonesia's Krakatoa erupted and massive ash clouds led to blue colored moons for years to follow.

Take a look at supermoons:

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Friday is the last blue moon until 2018
ARLINGTON, VIRGINIA - AUGUST 10: A supermoon rises above the U.S. Marine Corps War Memorial on August 10, 2014 in Arlington, Virginia. Tonight's supermoon, or perigee moon referring to its closest point to earth, is the second one of the summer. According to NASA, the moon appears 30 percent brighter and 14 percent bigger than normal. Another supermoon will appear September 9. (Photo by Win McNamee/Getty Images)
NEW YORK - AUGUST 10: The perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
NEW YORK - AUGUST 10: The perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
NEW YORK - AUGUST 10: The perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
NEW YORK - AUGUST 10: The perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
The perigee moon or 'supermoon' is seen above a US flag on the US Marine Corp War Memorial on August 10, 2014 in Arlington, Virginia. Tonght's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
MADRID, SPAIN - AUGUST 10: The supermoon surrounded by Madrid skyscrapers on August 10, 2014 in Madrid, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 10, 2014. (Photo by Gonzalo Arroyo Moreno/Getty Images)
PRAGUE, CZECH REPUBLIC - AUGUST 10: A full moon is seen over the Old Town Bridge Tower on August 10, 2014 in Prague, Czech Republic. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Matej Divizna/Getty Images)
The perigee moon or 'supermoon' rises above the US Marine Corp War Memorial on August 10, 2014 in Arlington, Virginia. Tonght's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
NEW YORK - AUGUST 10: A couple's silhouette as the perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
The sun sets as a couple lay in the park waiting for a perigee moon, also known as a supermoon, to appear in Madrid, Sunday, Aug. 10, 2014. (AP Photo/Andres Kudacki)
In this aerial photo, the moon peeks through clouds over Baton Rouge, La., Sunday, Aug. 10, 2014. The phenomenon, which scientists call a "perigee moon," occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Gerald Herbert)
A girl plays with a dog as a perigee moon, also known as a supermoon, rises in Madrid, Sunday, Aug. 10, 2014. The phenomenon, which scientists call a perigee moon, occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Andres Kudacki)
The supermoon is seen as it rises through the clouds behind the bronze Statue of Freedom by Thomas Crawford atop the U.S. Capitol, Sunday, Aug. 10, 2014, in Washington. The phenomenon, which scientists call a "perigee moon," occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Alex Brandon)
Light from a lamppost shines near the perigee moon, also known as a supermoon, in Madrid, Sunday, Aug. 10, 2014. The phenomenon, which scientists call a "perigee moon," occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Daniel Ochoa de Olza)
The moon appears behind a cross on the unfinished Serbian Orthodox church Christ the Saviour Cathedral, in Kosovo capital Pristina, Sunday, Aug. 10, 2014. The phenomenon, which scientists call a "perigee moon," occurs when the moon is near the horizon and appears larger and brighter than other full moons. (AP Photo/Visar Kryeziu)
The perigee moon or 'supermoon' is seen above the US Marine Corp War Memorial on August 10, 2014 in Arlington, Virginia. Tonght's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
The perigee moon or 'supermoon' is seen above a US flag on the US Marine Corp War Memorial on August 10, 2014 in Arlington, Virginia. Tonght's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
The perigee moon or 'supermoon' is seen on August 10, 2014 from Arlington, Virginia. Tonght's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. AFP PHOTO/Mandel NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images)
WASHINGTON, DC - AUGUST 10: In this handout image provided by NASA, a perigree full moon or supermoon is seen over the The Peace Monument on the grounds of the United States Capitol on August 10, 2014 in Washington, DC. Tonight's supermoon, or perigee moon referring to its closest point to earth, is the second one of the summer. According to NASA, the moon appears 30 percent brighter and 14 percent bigger than normal. Another supermoon will appear September 9. (Photo by Bill Ingalls/NASA via Getty Images)
WASHINGTON, DC - AUGUST 10: In this handout image provided by NASA, a perigree full moon or supermoon is seen behind clouds over the United States Capitol on August 10, 2014 in Washington, DC. Tonight's supermoon, or perigee moon referring to its closest point to earth, is the second one of the summer. According to NASA, the moon appears 30 percent brighter and 14 percent bigger than normal. Another supermoon will appear September 9. (Photo by Bill Ingalls/NASA via Getty Images)
WASHINGTON, DC - AUGUST 10: In this handout image provided by NASA, a perigree full moon or supermoon is seen over the Old Post Office and Clock Tower on August 10, 2014 in Washington, DC. Tonight's supermoon, or perigee moon referring to its closest point to earth, is the second one of the summer. According to NASA, the moon appears 30 percent brighter and 14 percent bigger than normal. Another supermoon will appear September 9. (Photo by Bill Ingalls/NASA via Getty Images)
The moon rises above Kansas City, Mo., during its closest point to the earth, called perigee, on Sunday, Aug. 10, 2014. It is often referred to as a Supermoon. August is the second of three consecutive months when the Supermoon occurs in 2014. The next Supermoon will occur Sept. 9. (John Sleezer/Kansas City Star/MCT via Getty Images)
MIAMI BEACH, FL - AUGUST 10: On the night of the supermoon, Rafael Fonseca plays soccer on August 10, 2014 in Miami Beach, Florida. In the second supermoon or perigee moon as it is also known of the summer, the moon appears 30 percent brighter and 14 percent bigger than normal. (Photo by Joe Raedle/Getty Images)
ATHENS, GREECE - 2014/08/10: People take to the streets to enjoy the Supermoon as it rises over Athens. August 10th marks the appearance of the Supermoon where Earth's moon appears brighter and bigger as it reaches it closest distance to Earth making 14% larger and 30% brighter than the typical Full Moon. (Photo by George Panagakis/Pacific Press/LightRocket via Getty Images)
ATHENS, GREECE - 2014/08/10: A view of the Supermoon rising over Athens as it passes over some ancient columns in the Monastiraki region of Athens. August 10th marks the appearance of the Supermoon where Earth's moon appears brighter and bigger as it reaches it closest distance to Earth making 14% larger and 30% brighter than the typical Full Moon. (Photo by George Panagakis/Pacific Press/LightRocket via Getty Images)
ATHENS, GREECE - 2014/08/10: Tourists and Greek people photograph themselves in front of Ancient Market ruins with the supermoon rising over it. August 10th marks the appearance of the Supermoon where Earth's moon appears brighter and bigger as it reaches it closest distance to Earth making 14% larger and 30% brighter than the typical Full Moon. (Photo by George Panagakis/Pacific Press/LightRocket via Getty Images)
SPENCER, NY - AUGUST 10: A supermoon rises over a house on August 10, 2014 in Spencer, New York. In the second supermoon or perigee moon as it is also known of the summer, the moon appears 30 percent brighter and 14 percent bigger than normal. (Photo by Justin Heiman/Getty Images)
RIO DE JANEIRO, BRAZIL - AUGUST 10: Birds fly past as a supermoon rises in the sky on August 10, 2014 in Rio de Janeiro, Brazil. In the second supermoon or perigee moon as it is also known of the summer, the moon appears 30 percent brighter and 14 percent bigger than normal. (Photo by Mario Tama/Getty Images)
The full moon, nicknamed 'the supermoon', rises at Ipanema beach in Rio de Janeiro, Brazil, on August 10, 2014. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. AFP PHOTO / YASUYOSHI CHIBA (Photo credit should read YASUYOSHI CHIBA/AFP/Getty Images)
TORRELODONES, SPAIN - AUGUST 10: A supermoon appears behind the Torrelodones Tower on August 10, 2014 in city of Torrelodones, near Madrid, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Pablo Blazquez Dominguez/Getty Images)
The full moon, nicknamed 'the supermoon', rises between the columns of the Planalto Palace in Brasilia, Brazil on August 10, 2014. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. AFP PHOTO/EVARISTO SA (Photo credit should read EVARISTO SA/AFP/Getty Images)
View of the full moon nicknamed 'the supermoon' in Ouro Preto, Brazil, on August 10, 2014. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. AFP PHOTO / Douglas MAGNO (Photo credit should read Douglas Magno/AFP/Getty Images)
PRAGUE, CZECH REPUBLIC - AUGUST 10: A full moon is seen through lion, Czech national symbol, on August 10, 2014 in Prague, Czech Republic. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Matej Divizna/Getty Images)
PRAGUE, CZECH REPUBLIC - AUGUST 10: A full moon is seen behind the lion, Czech national symbol and the part of decoration of bridge, on August 10, 2014 in Prague, Czech Republic. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Matej Divizna/Getty Images)
GLASTONBURY, UNITED KINGDOM - AUGUST 10: The moon rises above Glastonbury Tor on August 10, 2014 in Somerset, England. Tonight's supermoon, or perigee moon referring to its closest point to earth, is the second one of the summer. According to NASA, the moon appears 30 percent brighter and 14 percent bigger than normal. Another supermoon will appear September 9. (Photo by Matt Cardy/Getty Images)
TORRELODONES, SPAIN - AUGUST 10: A supermoon appears behind the Torrelodones Tower on August 10, 2014 in city of Torrelodones, near Madrid, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Pablo Blazquez Dominguez/Getty Images)
RIO DE JANEIRO, BRAZIL - AUGUST 10: A Catholic procession passes as a supermoon rises in the sky on August 10, 2014 in Rio de Janeiro, Brazil. In the second supermoon or perigee moon as it is also known of the summer, the moon appears 30 percent brighter and 14 percent bigger than normal. (Photo by Mario Tama/Getty Images)
The full moon, nicknamed 'the supermoon', rises over road near the town of Bitola on August 10, 2014. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth.AFP PHOTO / ROBERT ATANASOVSKI (Photo credit should read ROBERT ATANASOVSKI/AFP/Getty Images)
WASSENAAR, NETHERLANDS - AUGUST 10: (EDITORS NOTE: Image is composed of multiple exposures and converted to black and white. No colour version available) A full moon is seen on August 10, 2014 in Wassenaar, The Netherlands. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Michel Porro/Getty Images)
the full moon nicknamed 'the supermoon' rises over the statue on the Charles Bridge on August 10, 2014 in Prague. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from EarthAFP PHOTO/ MICHAL CIZEK (Photo credit should read MICHAL CIZEK/AFP/Getty Images)
the full moon nicknamed 'the supermoon' rises over the statue on the Charles Bridge on August 10, 2014 in Prague. A supermoon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from EarthAFP PHOTO/ MICHAL CIZEK (Photo credit should read MICHAL CIZEK/AFP/Getty Images)
The 'supermoon' is seen rising above the Kuwait skyline on August 10, 2014. The 'supermoon' occurs when the moon reaches the closest point to the earth. AFP PHOTO/YASSER AL-ZAYYAT (Photo credit should read YASSER AL-ZAYYAT/AFP/Getty Images)
The 'supermoon' is seen rising above the Kuwait skyline on August 10, 2014. The 'supermoon' occurs when the moon reaches the closest point to the earth. AFP PHOTO/YASSER AL-ZAYYAT (Photo credit should read YASSER AL-ZAYYAT/AFP/Getty Images)
MADRID, SPAIN - AUGUST 10: A plane flights across the supermoon surrounded by a Madrid skyscraper on August 9, 2014 in Madrid, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Gonzalo Arroyo Moreno/Getty Images)
MADRID, SPAIN - AUGUST 10: A plane flights across the supermoon surrounded by two Madrid skyscrapers on August 9, 2014 in Madrid, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Gonzalo Arroyo Moreno/Getty Images)
The full moon descends behind the Nossa Senhora da Penha Church in Rio de Janeiro, Brazil, on August 10, 2014. In this time of the year the orb is at the closest point to the earth. Experts name this phenomenon the supermoon or perigee. AFP PHOTO / YASUYOSHI CHIBA (Photo credit should read YASUYOSHI CHIBA/AFP/Getty Images)
LABAJOS, SPAIN - AUGUST 09: A moon appears behind a Toro Osborne advertisement a day before the supermoon is full on August 9, 2014 near Labajos, in Segovia province, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Pablo Blazquez Dominguez/Getty Images)
LABAJOS, SPAIN - AUGUST 09: A moon appears behind the Toro Osborne advertisement a day before the supermoon is full on August 9, 2014 near Labajos, in Segovia province, Spain. In the second supermoon or perigee moon as it is also known of the summer, the moon will supposedly appear 30% brighter and 14% bigger than normal, with another due to appear in our skies on September 9, 2014. (Photo by Pablo Blazquez Dominguez/Getty Images)
NANGOKU, JAPAN - AUGUST 10: (CHINA OUT, SOUTH KOREA OUT) The 'Supermoon' rises after Typhoon Halong hit at Kochi Airport on August 10, 2014 in Nangoku, Kochi, Japan. The typhoon is moving north in the sea of Japan, the Japan Meteorological Agency has issued the high aleart for strong wind and high waves. (Photo by The Asahi Shimbun via Getty Images)
NEW YORK - AUGUST 10: The perigee moon or 'supermoon' is seen on August 10, 2014 from New York, United States. Tonight's supermoon is the largest and closest full moon of the year. It is 14 percent closer and 30 percent brighter than other full moons of the year, according to NASA. The supermoon on Sunday was the second in a trio of supermoons this summer, with one having happened on 12 July and the next one due to appear on 9 September. To have three in such close proximity is very rare and it is not expected that this will happen again until 2034. (Photo by Bilgin S. Sasmaz/Anadolu Agency/Getty Images)
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