June 20 Solstice Opes Northern Astronomical Summer and Southern Winter

Summary: With a north polar tilt toward the sun, the June 20, 2024, solstice simultaneously opes northern astronomical summer and southern astronomical winter.

Graphic of Northern Hemisphere's summer solstice depicts axial tilting toward sun favoring Northern Hemisphere and compares highest solar placements in the sky on equinoxes and solstices: via NOAA National Weather Service

With Earth's North Pole tilting toward the sun, the June 20, 2024, solstice simultaneously opes the astronomical seasons of summer in the Northern Hemisphere and winter in the Southern Hemisphere.

The June solstice in 2024 takes place Thursday, June 20, at 4:51 p.m. Eastern Daylight Time (EDT) in the Northern Hemisphere. The time of the Earth-wide event corresponds to Thursday, June 20, at 20:51 Coordinated Universal Time (UTC), the Earth's primary time standard, according to the U.S. Naval Observatory, Astronomical Applications Department's "Earth Seasons -- Equinoxes and Solstices -- 2023-2026," published on the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service website. The equinox occurs on Thursday, June 20, for the first three (UTC+1 through UTC+3) of the 14 time zones that lie east of UTC. It happens Friday, June 21, for the last nine (UTC+4 through UTC+14) of the time zones east of UTC. The equinox appears of Thursday, June 20, for all 12 time zones lying west of UTC, according to "Time Zone Converter -- Time Difference Calculator (Classic)," published on the Time and Date website.

A positive UTC offset, formatted as UTC+1 through UTC+14, references time zones east of UTC. A negative UTC offset, symbolized as UTC-1 through UTC-12, indicates time zones west of UTC. Time zones east of UTC are ahead of UTC. Time zones west of UTC lag behind UTC.

The June solstice pairs with the year's December solstice in opening the astronomical seasons of summer and winter. The December solstice flips the June solstice's hemispheric seasonal assignments. Accordingly, the December solstice initiates astronomical winter in the Northern Hemisphere and astronomical summer in the Southern Hemisphere.

"But what is the solstice exactly?" asks NASA Jet Propulsion Laboratory web producer, editor and writer Jessica Stoller-Conrad in "What Is a Solstice?" on the National Oceanic and Atmospheric Administration's (NOAA) SciJinks website. The solstices are associated with "imaginary lines on our planet," such as the equator, Earth's axis of rotation and the "special" tropical latitudinal circles of Cancer in the Northern Hemisphere and Capricorn in the Southern Hemisphere.

June's solstice links with the Northern Hemisphere's Tropic of Cancer. December's solstice connects with the Southern Hemisphere's Tropic of Capricorn. The year's two solstices represent a directly overhead sun at high noon, i.e., 12:00 p.m., at the respective circle of latitude. Accordingly, the sun appears directly above the Tropic of Cancer on the June solstice and directly above the Tropic of Capricorn on the December solstice.

These two imaginary circles mark, respectively, the northernmost and southernmost latitudes for a directly overhead sun at high noon. "Outside the tropic zones, whether to the south or north, the sun is never directly overhead," explains Jessica Stoller-Conrad.

The year's two solstices share responsibility for the astronomical seasons with the year's two equinoxes, which occur in March and September. The March equinox occasions astronomical spring in the Northern Hemisphere and astronomical autumn in the Southern Hemisphere. March's complement, September's equinox, ushers astronomical autumn in the Northern Hemisphere and astronomical spring in the Southern Hemisphere.

Equinoxes and solstices sequence alternately, every three months, in each year. The year's first equinox appears in March. Three months later, the year's first solstice happens in June. The second of the year's two equinoxes occurs three months later, in September. Finally, the second of the year's two solstices takes place in December, three months after September's equinox.

In 2024, as the successor of June's solstice, September's equinox is scheduled for Sunday, Sep. 22, 2024, at 8:44 a.m. EDT (12:44 UTC). September's equinox is timed for Monday, Sep. 23, for the last three (UTC+12 through UTC+14) of the 14 time zones lying east of UTC.

December's solstice occurs as the year's final astronomical season opener. In 2024, the year's last solstice is slated for Saturday, Dec. 21, at 4:21 a.m. Eastern Standard Time (EST) and at 09:21 UTC. December's solstice is slated for Sunday, Dec. 22, for the last three (UTC-10 through UTC-12) of the 12 time zones lying west of UTC.

The National Oceanic and Atmospheric Administration's (NOAA) GOES (Geostationary Operational Environmental Satellites) East and West satellites imaged Earth moments after the June 2019 solstice's occurrence Friday, June 19, at 1:54 a.m. Eastern Daylight Time (03:54 Coordinated Universal Time UTC): via NOAA NESDIS (National Environmental Satellite, Data, and Information Service)

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Graphic of Northern Hemisphere's summer solstice depicts axial tilting toward sun favoring Northern Hemisphere and compares highest solar placements in the sky on equinoxes and solstices: via NOAA National Weather Service @ https://www.weather.gov/unr/summer_solstice

The National Oceanic and Atmospheric Administration's (NOAA) GOES (Geostationary Operational Environmental Satellites) East and West satellites imaged Earth moments after the June 2019 solstice's occurrence Friday, June 19, at 1:54 a.m. Eastern Daylight Time (03:54 Coordinated Universal Time UTC): via NOAA NESDIS (National Environmental Satellite, Data, and Information Service) @ https://www.nesdis.noaa.gov/news/goes-east-and-west-see-the-summer-solstice

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