SkyScan Sky Notes

The Summer Solstice Is Almost Here

Every June, we hear that summer officially begins with the summer solstice. But why does summer sometimes begin on June 20 and other years on June 21? The answer comes from the precise geometry of Earth's journey around the Sun.

What Is the Summer Solstice?

The word solstice comes from Latin and is often translated as “sun standing still.” Around the solstice, the Sun's apparent movement northward in the sky slows, stops, and then begins moving southward again.

For the Northern Hemisphere, the summer solstice happens when Earth's North Pole is tilted most directly toward the Sun. This gives us the longest period of daylight of the year and marks the beginning of astronomical summer.

In 2026, the summer solstice occurs on Sunday, June 21, at approximately 4:24 a.m. EDT.

Why Doesn't Summer Begin on the Same Date Every Year?

Seasons do not begin on fixed calendar dates. Earth takes about 365.2422 days to complete one orbit around the Sun, which is why our calendar needs leap years to stay aligned with the seasons.

Because of that extra fraction of a day, the exact moment of each solstice and equinox shifts slightly from year to year. Depending on the year and your time zone, the first day of summer may fall on June 20 or June 21.

It's All About Earth's Tilt

A common misconception is that seasons are caused by Earth's distance from the Sun. They are not. The seasons are caused by Earth's axial tilt.

Our planet is tilted about 23.4 degrees as it orbits the Sun. In June, the Northern Hemisphere tilts toward the Sun, giving us longer days and a higher Sun in the sky. In December, it tilts away from the Sun, giving us shorter days and lower Sun angles.

The Longest Day Is Not Usually the Hottest Day

The summer solstice gives us the most daylight, but it is usually not the hottest day of the year. Land and oceans warm gradually, so the warmest weather often arrives in July or August.

What Happens After the Solstice?

After the solstice, daylight slowly begins to decrease. At first, the change is tiny, but it gradually adds up as Earth continues toward the autumnal equinox.