Spring Equinox Is Here, What Does It Mean?

Another year, another spring equinox. Astronomical spring will begin on Friday morning this week.

This equinox means that the sun's most intense rays will be directed at the equator.

When the sun’s rays do this, the Northern Hemisphere flips to astronomical spring. Along the East Coast, this happens at 10:46 a.m. EDT while the West Coast will start spring at 7:46 a.m.

If you remember us mentioning a spring already, you are not wrong.

(MORE: Meteorological Spring)

Meteorological spring began on March 1. This similar term is the three-month period where temperatures are, on average, climbing. We intentionally use March 1 since astronomical spring can shift slightly due to the Earth's tilt. I'll explain more below.

(MORE: Spring Temperature Outlook)

Astronomical spring, in contrast, floats in time and date due to slight wobbles in the Earth's axial tilt. Since the key to the start of spring is when the sun's rays cross from the Southern Hemisphere to the Northern Hemisphere, this can change the start date of spring to range from March 19-21.

It is at the moment that the sun moves across the equator that day and night are roughly balanced. Daylight will continue to increase during these spring months for us in the Northern Hemisphere.

Think of it this way: Instead of a tilt away from or toward the sun, the Earth's axis of rotation is perpendicular to the line connecting the centers of Earth and the sun during an equinox. Equinox does come from the root word equal, after all.

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Because of that, day and night are balanced to roughly 12 hours each all over the world. You can see this in the half-sunlit and half-nighttime (dark areas) satellite loop below.

From this point on, daylight in the Northern Hemisphere will gradually grow longer until the summer solstice, which occurs on June 21. That's because Earth will be in the process of tilting toward the sun in the Northern Hemisphere.

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And the opposite is true for you living in the Southern Hemisphere. If you’re reading us from Down Under, the March equinox marks the beginning of fall.

Daylight will now grow shorter until June's start of winter in places like Australia and South America. This is because as the Earth is tilting toward the sun for the Northern Hemisphere, it is tilting away from the sun in the Southern Hemisphere.

Jonathan Belles has been a graphics meteorologist and writer for weather.com for 9 years. His favorite weather is tropical weather, but also enjoys covering high-impact weather and news stories and winter storms. He's a two-time graduate of Florida State University and a proud graduate of St. Petersburg College.