As we welcome September 22, 2024, the equinox graces the Earth with a momentary balance between day and night. The word “equinox” is derived from the Latin words aequus (equal) and nox (night), perfectly encapsulating this unique celestial event. This year’s September equinox, often referred to as the autumnal equinox in the Northern Hemisphere and the vernal equinox in the Southern Hemisphere, marks a seasonal shift as the Sun crosses the celestial equator.
At precisely 6:44 AM UTC today, the Sun appeared directly above the equator, signaling the beginning of autumn for those above the equator and spring for those below it. On this day, nearly every place on Earth will experience about 12 hours of daylight and 12 hours of darkness, a rare equilibrium in our planet’s otherwise tilted dance around the Sun.
The equinox happens twice a year—once in March and once in September. These are the only two days when the Sun shines directly over the equator, resulting in nearly equal amounts of day and night across the globe.
- The March Equinox: Occurring around March 20 or 21 each year, this equinox marks the start of spring in the Northern Hemisphere and the beginning of autumn in the Southern Hemisphere. Also known as the vernal or spring equinox in the north, this event signals the return of longer days and shorter nights as the Earth tilts toward the Sun.
- The September Equinox: Falling on or around September 22 or 23, this equinox, like today’s, brings autumn to the Northern Hemisphere and spring to the Southern Hemisphere. As the Earth’s tilt shifts, those in the north prepare for cooler months, while those in the south welcome warmer weather.
These two equinoxes are critical turning points in the year, marking the transition between the extreme temperatures of summer and winter and the more temperate seasons of spring and fall.
The Earth’s axis is tilted about 23.5 degrees relative to its orbit around the Sun, causing the different amounts of daylight we experience throughout the year. The equinox is one of two moments annually when the Earth’s axis is not inclined toward or away from the Sun. This means the Sun illuminates both hemispheres equally, resulting in this fleeting balance.
After today, as the Earth continues its orbit, the Northern Hemisphere will tilt further away from the Sun, ushering in longer nights and shorter days as winter approaches. Meanwhile, in the Southern Hemisphere, the days will grow longer, heralding the warmer months of spring and summer.
How the Northern Hemisphere’s Winter Affects Northern Philippines
The tilt of the Earth not only shapes the seasons but also affects global weather patterns. In the Northern Hemisphere, as autumn deepens and winter approaches, cooler air masses start to dominate, bringing significant changes even to regions closer to the equator. One of these areas is the northern part of the Philippines, particularly the mountainous Cordillera region.
During the winter months in the Northern Hemisphere, the northeast monsoon, known locally as Amihan, brings cool winds down from East Asia, influencing the climate in the northern Philippines. The mountain ranges, particularly the Cordillera and Sierra Madre, experience much cooler temperatures due to the elevation and the influx of these cold winds. In places like Baguio, Sagada, and the freezing Atok and Madaymen, this results in a climate that is considerably cooler compared to the lowland regions. In fact, between December and February, temperatures can drop to as low as 10°C (50°F), offering a cooler respite in contrast to the tropical heat typically associated with the Philippines.
This phenomenon of cool air descending from the northern hemisphere’s winter creates a unique climatic pattern in the northern Philippines, where residents and visitors alike experience a distinctly cooler season, influenced by global shifts that originate thousands of kilometers away. – CCT
