Saturday, June 20, at 2:44 P.M. PDT. This date marks the official beginning of summer in the Northern Hemisphere, occurring when Earth arrives at the point in its orbit where the North Pole is at its maximum tilt (about 23.5 degrees) toward the Sun, resulting in the longest day and shortest night of the calendar year.
The timing of the June solstice is not based on a specific calendar date or time; it all depends on when the Sun reaches its northernmost point from the equator. Therefore, the solstice won’t always occur on the same day. Currently, it shifts between June 20, 21, and 22.
Although the day of the solstice has the most daylight hours of the year, in the Bay Area we will have 14:46 hours of daylight, the earliest sunrises of the year occur before the summer solstice. The exact timing will depend in part on your latitude: In the mid-latitudes of the Northern Hemisphere, it occurs about a week earlier than the June solstice.
The reason for the timing of sunrises is related to the inclination of the Earth’s rotational axis and Earth’s elliptical (rather than circular) orbit.
The latest sunsets of the year will occur several days after the solstice, again depending on latitude.
You may wonder why, if the solstice is the longest day of the year—and thus gets the most sunlight—the temperature usually doesn’t reach its hottest. The solstice marks the height of the sun, but the hottest weather comes a month or two later. That’s because the land and oceans have to warm up, too, before the truly hot summer heat can begin. This phenomenon is called the lag of the seasons.