A harvest moon is the full moon that occurs closest to the autumnal equinox, which marks the beginning of fall in the Northern Hemisphere. The harvest moon is special because it rises very soon after sunset for several evenings in a row, providing extra light in the evenings during the fall harvest season. But is a harvest moon also a “blood moon” or red moon? Let’s take a closer look.
What is a Harvest Moon?
As mentioned above, the harvest moon is the full moon that occurs closest to the autumnal equinox, which is typically around September 22-23. The harvest moon falls in September about once every three years, but can also occur in early October.
Here are some key facts about the harvest moon:
- Rises very soon after sunset, providing extra illumination in the evenings right after the sun goes down
- The timing has to do with the moon’s position relative to the horizon and the elongation of the moon’s orbit
- The harvest moon can rise 20-30 minutes earlier for several evenings than a typical full moon
- Provided extra light for farmers harvesting crops by lantern light in earlier eras
- Native American tribes also used the harvest moon to gather crops for winter
So in summary, the harvest moon is the full moon closest to the autumnal equinox, providing extra light in the evenings. But does it also appear red?
What is a Blood Moon or Red Moon?
A blood moon, also known as a red moon, occurs during a total lunar eclipse. A lunar eclipse happens when the Earth lines up directly between the sun and the moon, casting a shadow on the moon. Here are some key points about blood moons:
- The moon appears red or orange during the eclipse due to rays of sunlight passing through Earth’s atmosphere
- The same process that makes sunsets red causes the moon to appear reddish
- Lunar eclipses only happen during a full moon
- There are usually 2-3 total lunar eclipses per year, so red moons are not uncommon
The term “blood moon” is also sometimes used for a reddish-looking moon caused by dust, haze, or smoke in the atmosphere. But most of the time, a blood moon specifically refers to the coppery color seen during a total lunar eclipse.
Is a Harvest Moon a Blood Moon?
Now we can address the original question – can a harvest moon also be a blood moon, turning red instead of its usual golden color? And the answer is…
No, a harvest moon does not also appear red.
While a blood moon is always associated with a full moon, a harvest moon itself does not turn red or become a lunar eclipse. There are two main reasons for this:
- Harvest moons happen at a specific time of year, while eclipses can occur any time.
- Lunar eclipses require precise alignment between the Earth, sun and moon.
The harvest moon is defined by the timing – fall equinox, rather than any change in moon color. While the harvest moon can fall during an eclipse in rare cases, it does not turn red simply because it is a harvest moon.
When Can a Harvest Moon Coincide with a Lunar Eclipse?
While it’s not common, it is possible for a harvest moon to line up with a lunar eclipse and turn reddish in color. For this to happen, a total lunar eclipse has to occur within one day of the autumnal equinox.
Some past examples of a blood moon harvest moon:
- In 2015, a total lunar eclipse occurred on September 28, two days after the equinox.
- In 2024, a total lunar eclipse will occur on September 18, two days before the equinox.
So about once per decade, the timing works out for the harvest moon to also be a blood moon. But the vast majority of the time, harvest moons are not eclipses and do not appear red.
Why are Harvest Moons and Lunar Eclipses Unrelated?
To understand why harvest moons don’t necessarily coincide with eclipses, let’s look at the separate factors that cause each event:
What Makes a Harvest Moon:
|Autumnal equinox||Start of fall in Northern Hemisphere, around Sept 22-23|
|Full moon timing||Full moon occurs closest to the equinox date|
|Moonrise time||Moon rises soon after sunset around equinox due to position|
What Makes a Blood Moon:
|Full moon||Lunar eclipses only occur at full moon|
|Moon-Earth-Sun alignment||Precise lineup needed between celestial bodies|
|Passing through Earth’s shadow||Moon passes through Earth’s umbra, causing reddish color|
As you can see, the requirements are completely different! The harvest moon is based on certain times of year and moonrise times. Lunar eclipses rely on precise celestial alignment and entering Earth’s shadow. These factors are independent, so there is no strong link between the two phenomena.
Can Other Full Moons be Red?
While lunar eclipses are the most common cause of red moons, they aren’t the only possibility. Here are some other potential ways the full moon can take on a reddish hue:
- Lunar eclipse – Most common cause, as detailed earlier.
- Atmospheric conditions – Dust, smoke, or haze can scatter red light from the sun onto the moon.
- Forest fire smoke – Massive fires throw huge plumes of smoke high into the atmosphere.
- Ash and debris – After volcanic eruptions, ash clouds can also turn the moon red.
- Pollution – Air pollution and particles in the air can rarely color the moon as well.
So while lunar eclipses are the primary cause, other environmental factors can sometimes give the full moon a blood-red tint. But regardless of the mechanism, a regular old harvest moon does not qualify as a red moon.
In summary, while the harvest moon and blood moon sound similar, they are different astronomical phenomena:
- A harvest moon occurs in fall and provides extra light, but has no change in moon color.
- A blood moon is always connected to a total lunar eclipse and appears red.
- A harvest moon is not necessarily a blood moon, since the timing rarely lines up.
- But on very rare occasions, a harvest moon can coincide with an eclipse.
So next time you see an big, bright, golden full moon in September or October, that will be the harvest moon. For it to turn blood red, it would also need to fall on the same night as a total lunar eclipse, which only happens every decade or two. But regardless of its color, enjoy the sight of the harvest moon rising!