“When does spring begin? is a more confusing question than you might think. Turns out it depends on who you ask.
When does spring start? March 1 or March 20?
Most people can say that March 20, the date of this year’s vernal equinox, marks the beginning of spring in 2022. But for a meteorologist, the answer is March 1.
Astronomical seasons have been around for thousands of years. They are dictated by the earth’s orbit around the sun and the sun’s ever-changing angle relative to the earth’s surface (thanks to our planet’s tilted axis). The two equinoxes – vernal and autumnal – and the two solstices – summer and winter – mark the divisions between the astronomical seasons. Weather seasons, on the other hand, are defined more by climate than by astronomy. These are blocks of equal three-month periods that coincide with the hottest, coldest, and “transitions” of the year.
Astronomically speaking, spring begins at the vernal equinox, which is the point in Earth’s orbit where the sun is directly above the equator on its journey higher in the northern hemisphere sky. Each year, the vernal equinox falls somewhere between March 19 and March 21. This year, it’s March 20 — at 11:33 a.m. ET to be precise.
Similarly, summer, fall, and winter begin at specific points in Earth’s orbit:
- Beginning of summer: the summer solstice, from June 20 to June 22 each year. This is when the sun is positioned directly above the Tropic of Cancer in the northern hemisphere. It marks the highest position of the sun above our heads for those of us in the United States, and it also marks the day with the greatest amount of daylight. This year, the summer solstice is June 21 at 5:13 a.m.
- Beginning of Autumn: Autumn begins either on September 22 or September 23, depending on when the autumnal equinox of a given year occurs. The autumnal equinox is the point when the sun is directly overhead the equator, like in early spring, but in this case the sun gradually drops in the northern hemisphere sky and colder temperatures are on their way.
- Beginning of winter: The winter solstice marks the beginning of winter. This happens every year between December 20 and 23. This year, it will happen at 4:47 p.m. on December 21. This marks the point where the sun is directly above the Tropic of Capricorn in the Southern Hemisphere. This is when the sun is at its lowest point in the northern hemisphere sky, and it marks the day with the least daylight in the year. This also signals the coldest period of weather for us in the United States.
The beginning and end of astronomical seasons vary from year to year, making them slightly inconsistent from a record-keeping perspective. This is where meteorologists come in.
Meteorologists define spring, and the seasons in general, in equal chunks of three months that mark the hottest, coldest, and most transient periods of weather for a region. This is a more consistent method for defining seasons and helps with record keeping.
Here is how the seasons are divided meteorologically:
- Winter: December 1 to February 28 – the three coldest months of the year.
- Spring: March 1 to May 31 – The regular three-month transition from cold to warm.
- Summer: June 1 to August 31 – The three hottest months of the year.
- Fall: The regular three-month transition from warm to cold.
Weather season definitions are simpler, more consistent, and more logically define the calendar year based on temperature. Scientifically, weather seasons are useful for comparing weather conditions from year to year. Because the timing is the same every year, all comparisons are apples to apples, if you will.
As the definitions above indicate, spring is a time of transition in New York. Temperatures rise steadily from start to finish. In fact, the transition is quite impressive. Average high temperatures at the start of the season are in the mid 40s. By the end of the season we are 30 degrees warmer, with highs averaging in the mid 70s. For those of you who get tired of our winter cold, that’s a reason to celebrate!