Old Farmer’s Almanac
Summer days are here. Summer begins with the solstice today, marking the astronomical first day of summer in the Northern Hemisphere. What exactly is the summer solstice? Is it really the longest day of the year? Welcome the solstice with some interesting facts and folklore.
The June Solstice
In the Northern Hemisphere, the June solstice (aka summer solstice) occurs when the sun travels along its northernmost path in the sky. This marks the astronomical start of summer in the northern half of the globe. (In the Southern Hemisphere, it’s the opposite: the June solstice marks the astronomical start of winter when the sun is at its lowest point in the sky.)
When is the Summer Solstice?
The June solstice occurs tonight at 9:42 p.m. CDT.
Solstice comes from the Latin words sol (“sun”) and sistere (“to stand still”). Due to Earth’s tilted axis, the sun doesn’t rise and set at the same locations on the horizon each morning and evening; its rise and set positions move northward or southward in the sky as Earth travels around the sun through the year.
Also, the sun’s track in the sky becomes higher or lower throughout the year. The June solstice is significant because the sun reaches its northernmost point in the sky at this time, at which point the sun’s path does not change for a brief period of time.
After the solstice, the sun appears to reverse course and head back in the opposite direction. The motion referred to here is the apparent path of the sun when one views its position in the sky at the same time each day, for example, at local noon.
Over the year, its path forms a sort of flattened figure eight, called an analemma. Of course, the sun itself is not moving (unless you consider its orbit around the Milky Way galaxy); instead, this change in position in the sky that we on Earth notice is caused by the tilt of Earth’s axis as it orbits the sun, as well as Earth’s elliptical, rather than circular, orbit.
Does the Solstice Always Occur on the Same Day?
The timing of the June solstice is not based on a specific calendar date or time; it all depends on when the sun reaches its northernmost point from the celestial equator. Therefore, the solstice won’t always occur on the same day. Currently, it shifts between June 20, 21, and 22.
The Year’s Longest Day
The Summer Solstice is the day with the longest period of sunlight. Notice how the sun appears highest in the sky at the solstice; its rays strike Earth at a more direct angle, causing the efficient warming we call summer.
For those locations at the Tropic of Cancer and northward, the sun is highest in the sky on the June solstice, and you’ll notice that your shadow (at local, or solar, noon, not clock-time noon) is the shortest that it will be all year (in fact, at the Tropic of Cancer there will be no shadow). [Local noon is when the sun crosses the local meridian (an imaginary line between the North and South poles) and is highest in the sky for the day.]
Frequently Asked Questions
Q: Why Doesn’t the Summer Solstice Fall on the Same Date Each Year?
A: The summer solstice in the Northern Hemisphere ranges in date from June 20 to 22. This occurs in part because of the difference between the Gregorian calendar system, which normally has 365 days, and the tropical year (how long it takes Earth to orbit the sun once), which has about 365.242199 days.
To compensate for the missing fraction of days, the Gregorian calendar adds a leap day about every 4 years, which makes the date for summer jump backward. However, the date also changes because of other influences, such as the gravitational pull from the Moon and planets, as well as the slight wobble in Earth’s rotation.
Q: Why isn’t the Summer Solstice — the Longest Day of the Year — Also the Hottest Day of the Year?
A: Earth’s atmosphere, land, and oceans absorb part of the incoming energy from the sun and store it, releasing it back as heat at various rates. Water is slower to heat (or cool) than air or land.
At the summer solstice, the Northern Hemisphere receives the most energy (highest intensity) from the sun due to the angle of sunlight and day length. However, the land and oceans are still relatively cool due to spring temperatures, so the maximum heating effect on air temperature is not felt just yet.
Eventually, the land—and especially the oceans—will release stored heat from the summer solstice back into the atmosphere. This usually results in the year’s hottest temperatures appearing in late July, August, or later, depending on latitude and other factors. This effect is called seasonal temperature lag.
Q: What is Midsummer Day (June 24)?
A: Historically, Midsummer Day marked the midpoint of the growing season, halfway between planting and harvest. It is traditionally known as one of four “quarter days” in some cultures — folks celebrate by feasting, dancing, singing, and preparing for the hot summer days ahead.
Many northern people also celebrate a solstice holiday known as Midsummer’s Day on June 24, which is one of the four ancient quarter days of the year. The eve prior is called Midsummer’s Eve, marking the shortest night of the year.
A common way to celebrate is to have a bonfire party! After all, these northern people have emerged from some long, dark winters. In the Austrian state of Tyrol, torches and bonfires are lit up on mountainsides, which is a stunningly beautiful sight.
According to ancient Latvian legend, Midsummer’s Eve (St. John’s Eve) on June 23 is spent awake by the glow of a bonfire and in pursuit of a magical fern flower — said to bring good luck — before cleansing one’s face in the morning dew.
Solstice Fun Facts
• The solstice does not bring the earliest sunrise
Although the day of the solstice has the most daylight hours of the year, the earliest sunrises of the year occur before the summer solstice. The exact timing will depend in part on your latitude: In the mid-latitudes of the Northern Hemisphere, it occurs about a week earlier than the June solstice.
The reason for the timing of sunrises is related to the inclination of the Earth’s rotational axis and Earth’s elliptical (rather than circular) orbit.
The latest sunsets of the year will occur several days after the solstice, again depending on latitude.
• The sun sets more slowly at the solstice
Did you know that the sun actually sets more slowly around the time of a solstice, in that it takes longer to set below the horizon? This is related to the angle of the setting sun.
The farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. (Conversely, it’s faster at or near the equinoxes.) Bottom line, enjoy those long, romantic summertime sunsets at or near the solstice.
