TAMPA, Fla. (WFLA) — The summer solstice marks the official start to the (astronomical) summer season and typically occurs on June 20th, 21st, or the 22nd every year.
It is the day with the longest amount of daylight in the Northern Hemisphere and shortest amount of darkness.
Earth has four different seasons due to the 23.5 degrees tilt of the earth’s axis. The tilt remains unchanged throughout the year meaning half the year, the north pole is tilted more toward the sun and the other half it is tilted away.
The start of each season is determined by the position of the earth in orbit around the sun and which direction the tilt is pointing.
The day and exact moment in time the summer solstice (for the northern hemisphere) is determined is when the sun reaches its highest latitude or the point at which it is as far north from the equator as it will get all year.
At this moment, the sun is directly in line with, or overhead of, the imaginary line circling the globe 23.5 degrees north of the equator, known as the tropic of cancer.
Another way to look at it is when Earth’s North Pole is pointed toward the sun and is receiving the most amount of sunlight possible. This point also marks the start of astronomical winter for the Southern Hemisphere, as the South Pole is pointed as far away from the sun as possible and receives no sunlight during this time.
This year, (in 2021), the summer solstice occurs at 11:32 pm ET on June 20. It occurs at the same time around the world.
Tampa will receive 13 hours, 54 minutes and 54 seconds of daylight, making it the day with the most amount of daylight and shortest night of the year.
Even though every day from here until the winter solstice in December will get shorter, the summer heat is just turning on and temperatures will stay warm for the next few months. The sun’s angle in the sky will slowly sink back south, but because the energy isn’t mostly being used to warm everything back up from the winter anymore, it is used to heat up the Northern Hemisphere.
Meteorological summer began June 1st and runs through August and is determined by the warmest months of the year. This makes it easier for meteorologists to compare seasons because each of the four is more equal in length and the start and end at the same date every year. Temperature and rainfall data can be analyzed more fairly and comparisons can be drawn more easily.
This is compared to the astronomical seasons which vary in length from season to season and from year to year because the earth’s orbit is an ellipse, rather than a circle, around the sun.
To prove that the tilt is what causes the seasons, it is important to know that the earth is at its closest point physically to the sun on the orbit in early January, which is when it is colder in the Northern Hemisphere.