Understanding the First Day of Spring: The Equinox Explained

The first day of spring aligns with the spring equinox this Thursday morning, occurring at 5:01 a.m. EDT on the East Coast and 2:01 a.m. PDT on the West Coast. This event marks the start of astronomical spring, while meteorological spring began on March 1. The equinox signifies equal day and night durations globally, and for the Southern Hemisphere, it initiates fall.

The first day of spring is set to occur on Thursday morning with the arrival of the spring equinox. This astronomical event happens when the sun’s rays align with the Earth’s equator, marking the transition into spring for the Northern Hemisphere at specific times: 5:01 a.m. EDT along the East Coast and 2:01 a.m. PDT on the West Coast.

Contrarily, meteorological spring, which commenced on March 1, denotes a standardized three-month period characterized by rising temperatures. This calendar-based definition provides meteorologists with a consistent framework for record-keeping while allowing for clear seasonal transitions.

Astronomical spring’s timing fluctuates annually, occurring between March 19 and March 21. At this spring equinox, day and night durations equalize globally, indicating a pivotal moment where daylight begins to lengthen and will continue to do so until the summer solstice on June 20.

During the equinox, the Earth’s axis remains perpendicular to the line connecting the Earth and the sun, resulting in nearly equal hours of day and night worldwide. For regions in the Southern Hemisphere, including Australia and South America, the March equinox signifies the onset of fall, as daylight will diminish moving towards winter in June.

In summary, the onset of spring varies between meteorological and astronomical definitions, with the latter heralding a more dynamic and shifting timeline based on celestial events. The arrival of the spring equinox marks significant changes in daylight duration, with a balance of day and night experienced globally. Consequently, while spring begins in the Northern Hemisphere, the Southern Hemisphere enters its autumnal season.

Original Source: weather.com