Mar 19, 2024
Want to welcome the flowers and showers of spring the moment it arrives? If you live in the US, set your clocks for 11:06pm EDT tonight, and you’ll be ready.
The onset of spring is also known as the vernal equinox ("equi": equal and "nox": night). It heralds the moment the sun’s rays shine straight across the equator. That’s the invisible line forming a belt around the widest part of the Earth. For folks in the Northern Hemisphere, the equinox marks the onset of warmer weather and longer days. This happens as the sun’s rays shine directly on the upper part of our tilted planet.
Between March and June, the strength of the sun’s power will travel northward. It'll reach its apex around Thursday, June 20. That's the summer solstice. Then the sun's power will dip back toward the equator as the Northern Hemisphere heads toward fall (the autumnal equinox in September).
Of course, some might be confused why the US is spring-ready on March 19 this year. Usually, the season shifts on the 20th or 21st. For the early arrival, blame February 29. Since it’s a leap year, we crammed an extra day into the calendar to account for the difference in our yearly reckoning and the actual trip Earth takes around the sun. So spring seems early. But it’s arriving right when it always does.
One other odd event: if you live with a meteorologist, they might’ve started acting as though spring had sprung a long time ago. That’s because weather buffs key into “meteorological spring,” rather than “astronomical spring.” The “meteorological spring” begins March 1 each year. It's based on changing weather patterns in the Northern Hemisphere rather than Earth's position relative to the sun.
Reflect: What are some of your favorite springtime traditions or holidays?
How Earth's Tilt Causes Seasons
This video shows how Earth's axial tilt causes sunlight to reach the Northern and Southern Hemispheres differently, depending on the time of year.
Are Southern Hemisphere Seasons More Severe?
This video explains how the oceans act as a moderator to prevent more severe seasonal temperatures in the Southern Hemisphere, even though it's closer to the sun in the summer and further from the sun in the winter.
Climate Change Toolkit: Solar Energy & Soil Temperature
This outdoors experiment is an effective way for students to learn how soil absorbs solar energy at various depths, times of day, and during different seasons.
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