Today is the June Solstice, the first day of summer in the northern hemisphere. The new season officially begins at 16:38 UTC, which is 12:38 PM Eastern Daylight Time.

The astronomical seasons are produced by the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the summer months, the northern half of the Earth is angled toward the sun. This position allows the northern hemisphere to receive the sun’s energy at a more direct angle and produces our warmest temperatures of the year.

Since the winter solstice in December, the arc of the sun’s apparent daily passage across the sky has been moving northward and daylight hours have been increasing. Today, it reached its northern most position at the Tropic of Cancer (23.5° north latitude) marking the “longest day” of the year. This observable stop is where today’s event takes its name. Solstice is a word derived from Latin meaning, “sun stands still”.

Now, the sun will start to move southward again in our sky and daylight hours will slowly decrease.

Earth’s solstices and equinoxes. Image Credit: NASA

The Sun is directly overhead at 23.5° North latitude (Tropic of Cancer) on the Summer Solstice. Image Credit: NASA