This weekend, a Thunder Moon Eclipse will be visible from North America.

By Jamie Carter
June 30, 2020
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A Thunder Moon is rising on Independence Day — and it’s going to look a little strange.

In addition to a full moonrise at dusk, this year’s July 4 celebrations also coincide with a penumbral lunar eclipse. It comes two weeks after a ring of fire solar eclipse on the summer solstice in Africa and Asia, and a month after the Strawberry Moon Eclipse that was best seen in Europe, Africa, and Asia.

Now it's North America's turn to see an extra-special full moon — a Thunder Moon Eclipse.

What is a Thunder Moon Eclipse?

A Thunder Moon Eclipse is a penumbral lunar eclipse that occurs in July. The name comes from the summer storms that occur around July’s full moon, giving it the name "Thunder Moon." It’s also called the "Buck Moon" because male deer lose their antlers this month.

The Thunder Moon (or Buck Moon) will drift into Earth’s outer shadow in space — creating a penumbral eclipse. About a third of the full moon will be covered by the Earth’s shadow, so it won’t be a hugely obvious effect, but it’s definitely worth looking up at the full moon at the right time.

When is the Thunder Moon Eclipse?

There are two specific times to watch this month’s full moon at its best — moonrise and "maximum eclipse." If you want to watch the Thunder Moon appear on the eastern horizon — a dramatic sight indeed — take a look just after 8:23 p.m. EDT on July 4 if you're in New York, and look up in the minutes after 8:06 p.m. PDT that evening if you're in Los Angeles.

Next comes the eclipse, which is a global event taking 2 hours and 45 minutes. From New York, the best time to look will be 12:29 a.m. EDT on July 5, and the best time to look from Los Angeles will be 9:29 p.m. PDT on July 4.

Jesus Merida/SOPA Images/LightRocket via Getty Images

What is a penumbral lunar eclipse?

A penumbral lunar eclipse occurs when the Earth is almost, but not quite, positioned between the Sun and a full moon. As the moon drifts into the Earth’s shadow about 870,000 miles out in space, it loses its brightness. If it entered Earth’s central shadow — its dark umbra — all sunlight would be blocked, and the moon would go dark and reddish. That’s often known as a "blood moon." That’s not what’s happening on July 4. Instead, the full moon will enter the outer, fuzzy penumbral shadow, so only some of the sunlight will be blocked from reaching the full moon’s surface. It’s a strange, subtle sight.

When is the next lunar eclipse in North America?

North America will get to see another penumbral lunar eclipse on November 30, 2020, when a “Frosty Moon Eclipse” will be visible from across the continent. However, the next really good lunar eclipse — a total lunar eclipse — won’t be visible in North America until next spring when, on May 26, 2021, a "Blood Flower Supermoon Eclipse" will see the lunar surface swathed in a red color for an exciting 15 minutes. There will be a much longer total lunar eclipse a year later — the “Blood Flower Moon Eclipse” on May 16, 2022, when the moon will be completely red for a whopping 84 minutes.