Idaho local data guide

Daylight Duration in Boise During the Summer Solstice

During the summer solstice, typically occurring on June 21, Boise experiences its longest day of the year with approximately 15 hours and 29 minutes of daylight.

Updated with grounded research as of 2026-09-16.

The short answer

On the summer solstice in Boise, Idaho, residents experience approximately 15 hours and 29 minutes of daylight. This date, typically falling on June 21, marks the longest day of the year in the Northern Hemisphere, providing significantly extended evening light that remains a notable characteristic of the Boise summer experience.

Key facts

Typical Summer Solstice Daylight Duration
15 hours and 29 minutes
Summer Solstice Date
June 21

The Experience of Long Summer Days

Boise is widely recognized for its unusually late sunsets during the summer months. Because of the city's geographic position and its time zone, daylight often extends well into the evening, with the sun setting around 9:29 p.m. during the solstice. This extended light creates a unique environment for outdoor recreation, local dining, and community activities along the Boise River Greenbelt and in surrounding neighborhoods.

Geographic and Seasonal Context

The daylight duration is a result of the Earth's axial tilt toward the sun during the June solstice. While the 15-hour-plus days define the peak of summer, the seasonal shift is stark: Boise sees a significant variation in day length, with the winter solstice in December offering only about 8 hours and 59 minutes of daylight. This contrast is a primary factor in the distinct seasonal rhythm felt by residents in the Treasure Valley.

Planning for Sunshine

  • Boise averages over 200 sunny days annually, consistently ranking high among U.S. cities for clear and sunny weather.
  • Nautical twilight often lasts until nearly 11:00 p.m. during the summer solstice period, meaning even after the sun sets, the sky remains light for quite some time.
  • The combination of long days and a high-desert climate allows for prolonged outdoor activities, which is a significant draw for those relocating to the region.

Common questions

Does the exact daylight duration change from year to year?

While the duration remains approximately 15 hours and 29 minutes, it can shift by a minute or two depending on the specific calendar year and the exact timing of the solstice.

Is the summer solstice always on June 21?

In most years, the summer solstice falls on June 21, though the specific date and time can vary slightly due to the discrepancy between the Gregorian calendar and the Earth's orbital period.

Related Idaho questions

  • What is the daylight duration during the winter solstice in Boise?
  • When does the latest sunset occur in Boise?
  • How does Boise's summer daylight compare to other U.S. cities?

Sources and verification