When does summer start

The Four Seasons of the Year: Spring, Summer, Fall, Winter

When do the four seasons start and end—for spring, summer, fall, and winter in North America? Find equinox and solstice dates for 2022—plus, answers to common questions. Do you know which season is shortest?

Many folks assume the four seasons happen because the Earth is closer to the Sun in the summer (so it’s hotter) and then the Earth is farthest from the Sun in the winter (so it’s colder). This is incorrect. The Earth’s tilted axis causes the seasons. In fact, winter is when Earth is closest to the Sun (and visa versa). More on that in a moment.

Our year (12 months) is commonly divided into four seasons, with each lasting about three months (but not exactly).

1. Spring
2. Summer
3. Fall or Autumn
4. Winter

When Do the Seasons Start?

However, the dates when the seasons begin and end vary depending on whom you ask. Each season has both an astronomical start and a meteorological start. It sounds complicated, but trust us, it’s not!

• The astronomical start date is based on the position of the Sun in relation to the Earth.
• The meteorological start date is based on our 12-month civiil calendar as well as the annual temperature cycle. 

The Definition of a “Season”

Here is more explanation about how astronomers and meteorologists define seasons differently:

• The astronomical start of a season is based on the position of the Earth in relation to the Sun. More specifically, the start of each season is marked by either a solstice (for winter and summer) or an equinox (for spring and autumn). A solstice is when the Sun reaches the most southerly or northerly point in the sky, while an equinox is when the Sun passes over Earth’s equator. Because of leap years, the dates of the equinoxes and solstices can shift by a day or two over time, causing the start dates of the seasons to shift, too.
   
• In contrast, the meteorological start of a season is based on the annual temperature cycle and the 12-month calendar. According to this definition, each season begins on the first of a particular month and lasts for three months: Spring begins on March 1, summer on June 1, autumn on September 1, and winter on December 1. Climate scientists and meteorologists created this definition to make it easier to keep records of the weather, since the start of each meteorological season doesn’t change from year to year.

The Old Farmer’s Almanac is an astronomical “calendar of the heavens,” so our book has long followed the astronomical definition of the seasons based on the Sun and Earth!

What Causes the Seasons?

As mentioned at the start of this article, the Earth’s tilted axis causes the seasons. The axis is always tilted in the same direction. So, as the Earth orbits the Sun over the 12 months of the year, different parts of Earth get the Sun’s direct rays

Look at the diagram below. When the North Pole tilts toward the Sun, it’s summer in the Northern Hemisphere. And when the South Pole tilts toward the Sun, it’s winter in the Northern Hemisphere.

Why Has Date Changed for Start of Seasons?

You may have noticed that the first day of spring used to be a different date when you were younger than it is today. The dates actually shift over time. Why?  There are several reasons but the one that’s easy to understand is: The Sun doesn’t follow a human calendar!

While our Gregorian calendar was designed to match the time it takes for the Earth to complete one orbit around the Sun, it’s not exact. Specifically, it eliminates leap days in century years not evenly divisible by 400, such 1700, 1800, and 2100, and millennium years that are divisible by 4,000, such as 8000 and 12000.

Therefore, the dates of the equinoxes and solstices can shift by a day or two over time, which causes the start dates of the seasons to shift over time, too.

Why Are The Seasons Different Lengths?

It can sometimes feel like winter is dragging on forever, but did you know that winter is actually the shortest season of the year? (In the Northern Hemisphere, that is.)

Why? Thanks to the elliptical shape of Earth’s orbit around the Sun, Earth doesn’t stay the same distance from the Sun year-round. In January, we reach the point in our orbit nearest to the Sun (called perihelion), and in July, we reach the farthest point (aphelion). 

When Earth is closer to the Sun, the star’s gravitational pull is slightly stronger, causing our planet to travel just a bit faster in its orbit. For those of us in the Northern Hemisphere, this results in a shorter fall and winter, since we are moving faster through space during that time of the year. Conversely, when Earth is farthest from the Sun, it travels more slowly, resulting in a longer spring and summer. (The opposite is true in the Southern Hemisphere.)

In other words, it takes Earth less time to go from the autumnal equinox to the vernal equinox than it does to go from the vernal equinox to the autumnal equinox.

Due to all this, the seasons range in length from about 89 days to about 94 days. 

Source- https://www.almanac.com/content/first-day-seasons

When does summer start? Here’s why each season begins twice.

Some measure seasonal shifts by Earth’s position relative to the sun, while others use annual temperature cycles. Here’s the difference between astronomical and meteorological seasons.

Every year, weather forecasters welcome the arrival of summer on the first of June—while others contend that the summer really begins a few weeks later with the solstice, which falls on June 20, 21, or 22. So who is right about when the seasons begin and end?

It depends on why you’re asking. Seasons are defined in two ways: astronomical seasons, which are based on Earth’s position as it rotates around the sun, and meteorological seasons, which are based on annual temperature cycles. Both divide the year into spring, summer, fall, and winter—yet with slightly different start and end dates for each. Here’s what they mean and how to tell them apart.

Astronomical seasons

People have always looked to the skies to determine the season. Ancient Rome was the first to officially mark those seasons with the introduction of the Julian calendar. Back then, the seasons began on different days than the modern era because of discrepancies with the Gregorian calendar used primarily today. Now, the start of each astronomical season is marked by either an equinox or a solstice.

Equinoxes are when Earth’s day is split almost in half. They occur every six months in the spring and fall, when Earth’s orbit and its axial tilt combine so that the sun sits directly above the Equator. On an equinox, roughly half the planet is light while the other half is dark. As the new season progresses, the sun’s position continues to change—and, depending which hemisphere you live in, the days will get progressively lighter or darker until the arrival of the solstice.

Solstices mark the brightest and darkest days of the year. They are also driven by Earth’s tilt and mark the beginning of astronomical summer and winter. When the Northern Hemisphere is tilted toward the sun, it is brighter and feels like summer—while, at the same time, the Southern Hemisphere is tilted away from the sun, plunging it into a dark winter.

But this method of measuring the seasons presents some challenges. The solar year is approximately 365.2422 Earth days long, making it impossible for any calendar to perfectly sync with Earth’s rotation around the sun. As a result, astronomical seasons start on slightly different days and times each year—making it difficult to keep the climate statistics that are used in agriculture, commerce, and more. That’s why weather forecasters and climatologists turned to meteorological seasons instead.

Meteorological seasons

Since at least the 18th century, scientists have sought better methods of predicting growing seasons and other weather phenomena. Over time, that gave rise to the concept of meteorological seasons, which are more closely aligned with both annual temperatures and the civil calendar.

Meteorological seasons are far simpler than astronomical seasons. They divide the calendar year into four seasons that each last exactly three months and are based on the annual temperature cycle. Winter takes place during the coldest three months of the year, summer in the hottest three months, and spring and fall mark the remaining transition months.

In the Northern Hemisphere, that means the start date for each season is March 1 (spring), June 1 (summer), September 1 (fall), and December 1 (winter). In the Southern Hemisphere, the seasons are reversed; spring begins in September, summer in December, fall in March, and winter in June.

The consistency of meteorological seasons allows meteorologists to make the complex statistical calculations necessary to make predictions and compare seasons to one another. “Dealing with whole-month chunks of data rather than fractions of months was more economical and made more sense,” climatologist Derek Arndt told the Washington Post in 2014. “We organize our lives more around months than astronomical seasons, so our information follows suit.”

So when is the first day of summer? It isn’t June 1 or the summer solstice—it’s both.

Source- https://www.nationalgeographic.com/environment/article/history-science-of-meteorological-astronomical-seasons