A supermoon shines over Pendleton during a lunar eclipse in September 2015. Cloudy weather over Pendleton could get in the way of viewing the total lunar eclipse Sunday, May 15, 2022.

Cloudy weather looks to get in the way of Sunday night, May 15, of a total lunar eclipse over Northeastern Oregon.

A blood moon occurs during a total lunar eclipse, when Earth is positioned directly between the sun and the moon, hiding the latter from sunlight. This month’s full moon is also a supermoon, which seems slightly larger and brighter than usual, since it is at perigee, its closest point to Earth in its orbit.

Because the moon’s orbit is not a perfect circle, the moon is sometimes closer to the Earth than at other points during its path. On average, supermoons appear about 7% bigger and 15% brighter than a typical full moon, according to NASA.

The full moon in May is called the “flower” moon. Other names for May’s full moon are the corn planting moon and the milk moon, according to NASA.

At totality, the moon will reflect a faint, reddish glow, as red wavelengths of sunlight filter through our planet’s atmosphere onto the moon’s surface. During the eclipse, it also could appear shades of orange, yellow or brown.

“When this happens, the only light that reaches the moon’s surface is from the edges of the Earth’s atmosphere,” NASA explained. “The air molecules from Earth’s atmosphere scatter out most of the blue light. The remaining light reflects onto the moon’s surface with a red glow, making the moon appear red in the night sky.”

The eclipse begins at moonrise, 8:13 p.m., reaches maximum at 9:11 p.m. and ends at 11:50 p.m., for a duration of three hours and 38 minutes in Pendleton. The penumbral eclipse will actually start at 6:32 p.m., but the moon will be below the horizon at that time.

The combination of it being very low on the horizon and the total eclipse phase will make the moon dim. Thus, it will be difficult to view until it gets higher in the sky or the total phase ends.

The National Weather Service, however, is forecasting a 40% chance of showers and thunderstorms before 11 p.m. over Pendleton. The night looks to be mostly cloudy with a low around 50.