When does spring arrive in the northern hemisphere? It sounds like a simple question. For those of us who still have wall calendars, it’s printed in bold letters on a specific date. If unlike me, you’re fully in the 21st century, your phone or some other connected device typically tells you. In 2022, my calendar (and several reputable websites) tell me spring arrives on Sunday 20 March. Would it surprise you to learn that there’s more than one acceptable answer?
Astronomical Spring
This is the most common (at least for me) definition of spring. Known as the vernal equinox, it’s defined as the date when the increasing daylight hours are equal to the nighttime hours. It varies between 19 and 21 March.
Solar Seasons
Solar seasons are based on insolation, or the amount of sunlight reaching a given spot. These seasons are defined by the midpoints of the astronomical seasons. For example, the solar winter equals the darkest quarter of the year, which is centered around the winter solstice. Solar spring is defined as the quarter where the sunlight increases the fastest. Medieval Europeans used solar seasons. The Celtic festivals of Samhain (Halloween), Imbolc (Groundhog Day), Beltane (May Day), and Lughnasadh mark the beginning of the solar seasons. (These festivals along with the euinoxes & soltices play an important role in my Misaligned series)
Meteorological Seasons
While solar seasons use sunlight to divide the year, meteorological seasons use temperature. The hottest three months define summer, the coldest winter, and the times in between are spring and autumn. Using this definition, spring begins on 1 March and ends on 31 May. In the Finland and Sweden, meteorologists use a more precise definition known as thermal seasons based on the average daily temperature. Spring begins when the mean rises above 0 °C (32 °F). Spring ends when that temperature rises above +10 °C (+50 °F).
Ecological Seasons
As interesting as those various methods are, the onset of spring is more than a date. It marks the time when plants begin to blossom and animal activities change. These biological signs are the indicators of ecological spring. Ecological spring brings both good and less than good effects. On the plus side, the days are longer and it’s more pleasant to spend time outdoors. On the con side, allergies kick in for some and lawn care begins in earnest.
That brings us to our featured map courtesy of Jack Sillin (sillinweather.com)
How do you reckon spring? What do your favorite/least favorite aspects of spring?
As always thanks for reading.
Armen
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Note to Pay the Bills: The Celtic seasonal holidays play an important role in the Misaligned series. They mark the time when cross-dimensional interactions are most likely. Book #1, Penny Preston and the Raven’s Talisman features both Halloween and the winter solstice. If you’ve ever wondered how to mix theoretical physics and Welsh mythology in a YA fantasty story, you can learn more here or find links to purchase books here.