First Day of Summer Calculator — Summer Solstice Date Finder

First Day of Summer 2025: When Does Summer Start?

The first day of summer, also known as the summer solstice, marks the astronomical beginning of the summer season and the longest day of the year. In 2025, the summer solstice in the Northern Hemisphere falls on June 21, while the Southern Hemisphere experiences its summer solstice in December. Use our calculator above to find the exact date and time for any year between 2000 and 2040.

What Is the Summer Solstice?

The summer solstice is an astronomical event that occurs when the Sun reaches its highest point in the sky at solar noon. Earth's axial tilt of approximately 23.44 degrees is maximally inclined toward the Sun, resulting in the longest period of daylight and the shortest night of the year. The word "solstice" comes from Latin sol (sun) and sistere (to stand still), because for a few days around the solstice, the Sun appears to rise and set at nearly the same points on the horizon.

Astronomical vs Meteorological Summer

There are two ways to define the start of summer. Astronomical summer is based on the Earth's axial tilt and begins on the date of the summer solstice, which varies between June 20–22 in the Northern Hemisphere and December 20–23 in the Southern Hemisphere. Meteorological summer follows a fixed calendar and always starts on June 1 in the Northern Hemisphere and December 1 in the Southern Hemisphere, making it easier for weather record-keeping and climate comparisons.

When Is the Summer Solstice?

In the Northern Hemisphere, the summer solstice occurs around June 20, 21, or 22 each year. In the Southern Hemisphere, the summer solstice occurs around December 20, 21, 22, or 23. The exact timing depends on the Earth's orbital position and can shift slightly due to leap years and other gravitational factors. Use our interactive tool above to see the precise UTC date and time for any year from 2000 to 2040.

Why Does the Date of the Solstice Change?

The date of the solstice varies because the Earth's orbit around the Sun takes approximately 365.25 days, while our calendar year is 365 days (with leap years adding an extra day every four years). This mismatch causes the solstice to shift by about 6 hours each year, with leap years resetting the cycle. Additionally, gravitational perturbations from other planets slightly affect Earth's orbit, introducing minor variations in solstice timing.

Traditions and Celebrations Around the Summer Solstice

Many cultures celebrate the summer solstice with festivals and traditions. In Scandinavia, Midsummer is celebrated with maypole dancing, bonfires, and feasting. Thousands gather at Stonehenge in England each June to watch the sunrise align with the ancient monument. In Peru, the Inti Raymi festival honors the Sun god with elaborate ceremonies. Modern celebrations include beach trips, barbecues, and enjoying the longest daylight hours of the year.

Related Seasonal Tools

Interested in the other seasonal transitions? Check out our First Day of Spring, First Day of Autumn, and First Day of Winter calculators to find the exact dates of every equinox and solstice throughout the year.

Frequently Asked Questions

What is the exact date of the summer solstice in 2025?

In the Northern Hemisphere, the summer solstice in 2025 occurs on June 21. In the Southern Hemisphere, the summer solstice occurs in December 2025. Use the calculator above to see the exact UTC time for your selected year and hemisphere.

Is the first day of summer always June 21?

No, the summer solstice can occur on June 20, 21, or 22 in the Northern Hemisphere, depending on the year. The date varies due to the difference between the calendar year (365 days) and the astronomical year (approximately 365.25 days), as well as leap year cycles.

Why is the summer solstice the longest day of the year?

The summer solstice is the longest day of the year because Earth's axial tilt is maximally inclined toward the Sun in the respective hemisphere. This means the Sun follows its longest path across the sky, resulting in the maximum amount of daylight hours. After the solstice, days gradually become shorter.

Is the summer solstice the hottest day of the year?

Despite having the longest day, the summer solstice is usually not the hottest day of the year. Due to "seasonal lag," oceans and land masses continue absorbing and releasing heat, so peak temperatures typically arrive 4 to 6 weeks after the solstice, in late July or early August in the Northern Hemisphere.

When does meteorological summer start?

Meteorological summer starts on June 1 in the Northern Hemisphere and December 1 in the Southern Hemisphere. This fixed-date system is used by meteorologists and climatologists to simplify seasonal record-keeping, as it aligns with the calendar months and allows for consistent comparisons of weather data across years.

How many hours of daylight are there on the summer solstice?

Daylight hours on the summer solstice depend on your latitude. At the equator, there are about 12 hours 7 minutes. At 40 degrees latitude (New York, Madrid), approximately 15 hours. At 50 degrees (London, Paris), about 16 hours 21 minutes. Above the Arctic Circle, the sun does not set at all — 24 hours of continuous daylight known as the midnight sun.

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First Day of Summer