Equinox about to make another return

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Conditions across the Inland Northwest have certainly become more like autumn. However, fall doesn’t officially start until next Monday, Sept. 23, at 12:50 a.m.

The first day of fall is also known as the Autumnal Equinox in the Northern Hemisphere. In the Southern Hemisphere, it will be their first day of spring. This is an astronomical event where the sun is directly overhead at the earth’s equator.

On Dec. 21, 2019, our first day of winter, the sun will be directly overhead in the Southern Hemisphere at 23.5 degrees south, the Tropic of Capricorn, their first day of summer. Then in March, we observe the Vernal Equinox, or the first day of spring, when the sun is once again directly overhead at the equator. By next summer, the sun will be overhead at 23.5 degrees north, or the Tropic of Cancer, which is why we get the longer daytime hours. Residents here in North Idaho will never see the sun directly overhead as we are too far to the north.

Most of you probably learned in school that we have seasons because the Earth is tilted on its axis by approximately 23.5 degrees. In our summer, the Northern Hemisphere is tilted toward the sun, allowing us to receive more direct solar radiation and hotter weather. In the winter, the Northern Hemisphere is tilted away from the sun. That’s why we have shorter daylight hours and a lower sun angle. Distance from the sun has very little to do with seasonal changes in temperature, as the earth is closer to the sun during our winter season, by about 3 million miles. It’s the tilt that makes all the difference for our four seasons.

During the equinoxes of both spring and fall, the Earth’s tilt has little effect based on our position in the orbit around the sun. During these times, every point on our planet has about 12 hours of day and night. The reasons the times are not exactly 12 hours apart on the first day of fall are complex. Our location in a particular time zone, elevation and the fact that the sun is not a singular point in space are some of the explanations.

The equinoxes as well as the summer and winter solstice (the first days of summer and winter) have many myths and traditions that have played a role in human cultures. Many people around the world have harvest celebrations and holidays to mark this month’s equinox.


One of the most amazing sights is the large pyramid at Chichen Itza, near Cancun, Mexico. The massive structure was constructed by the Mayan civilization and serves as a visual symbol for day and night. On the exact day of every equinox, September and March, the late-afternoon sun will create a snake of sunlight, or the illusion of a feathered serpent, that slowly moves down the staircase of the pyramid. It’s also quite amazing that the Mayans used advanced astronomical calculations over 1,000 years ago to create this structure.

Cliff and I were lucky enough to see this structure at our first seminar back in 1991. The pyramid and region are an amazing sight and I understand why this pyramid was named as one of the Seven Wonders of the New World.

The first day of fall is also linked to Greek mythology. According to the myth, Persephone was the queen of the underworld and the daughter of Zeus and Demeter, who was the goddess of harvest and fertility. Persephone was abducted from her mother and taken to the underworld to be the wife of Hades, the king of the underworld.

Demeter searched for her daughter and soon discovered where she had gone. With little help from Zeus, she left her duties of harvest and fertility and the earth’s harvests were failing. Therefore, a deal was reached that Persephone would spend 6 months in the underworld and 6 months on Earth with Demeter.

So, based on the myth, the fall and winter seasons are the result of Persephone living with her husband Hades as her mother would be sad and the land would not be fruitful. In the spring, Persephone returns to Earth and the land would become fertile again.


In terms of our local weather, we’ve had some very nice weather this past week. Cliff and I still see a pattern of sun and showers this month as precipitation totals should be close to the normal of 1.48 inches. Then, conditions are expected to turn wetter than normal as we move further into the fall season, with above average moisture totals forecast for the winter of 2019-20.

Once again, we need a “La Nina,” the cooler-than-normal sea-surface temperature event in the south-central Pacific Ocean, along with very low sunspot activity for the big snows this winter. Right now, sunspots on the sum are few and far between. Ocean waters are cooling, so we’ll have to wait and see.

• • •

Contact Randy Mann at randy@longrangeweather.com

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