First supermoon of 2021 nigh

By Bruce McClure

Contrasting a full supermoon with a micro-moon. Image APOD/Stefano Sciarpetti

Around the world, the moon will look full to the eye on the nights of April 26 and 27, 2021. However, the crest of the full moon will fall on April 27 at 03:31 UTC.

In United States times zones, that translates to April 26 at 11:31 p.m. Eastern, 10:31 p.m. Central, 9:31 p.m. Mountain and 8:31 p.m. Pacific.

In North America, we call the April full moon the Pink Moon. This April full moon presents the first in a “season” of three straight full moon supermoons. Overall, this April full moon gives us the second-closest full moon of the year.

Here are the distances (as measured between the centers of the moon and Earth) for the three upcoming full moon supermoons:

  1. April 27, 2021: 222,212 miles (357,615 km)
  2. May 26, 2021: 222,089 miles (357,462 km)
  3. June 24, 2021: 224,662 miles (361,558 km)

In contrast, the most distant and smallest full moon of the year will fall on December 19.

Sometimes called a micromoon, it’ll be 252,235 miles (405,932 km) away. That’s a whopping 30,118 miles (48,470 km) farther away than the year’s closest and biggest full moon on May 26.

Some people prefer to call a full supermoon a perigean full moon. That’s when the full moon and lunar perigee – the moon’s closest point to Earth in its monthly orbit – closely coincide for a few months. This April full moon occurs about 12 hours before the moon sweeps to lunar perigee. Next month, the May full moon will turn full some nine hours after the moon swings to perigee. April and May feature the only two months in 2021 whereby full moon and perigee occur less than 24 hours apart.

What’s more, Earth’s oceans feel the extra pull of these supermoons.

All full moons (and new moons) combine with the sun to create larger-than-usual tides, called spring tides. But closer-than-average full moons  – that is, supermoons – elevate the tides even more.

These extra-high spring tides are wide ranging. High tides climb up especially high, and, on the same day, low tides plunge especially low. Experts call these perigean spring tides, in honor of the moon’s nearness. If you live along an ocean coastline, watch for them! They typically follow the supermoon by a day or two.

Do extra-high supermoon tides cause flooding? Maybe yes, and maybe no.

Flooding typically occurs when a strong weather system accompanies an especially high spring tide.

No matter where you live worldwide, watch for the full moon to shine from dusk until dawn.