Seasonal figures below use a 2025 reference year. Choose a date in the planner above for that day’s times, golden hour, twilight, and daylight milestones.
Seasonal Sun Milestones in Mercer Island
Mercer Island's 9 PM sunsets run from about June 2 to July 17 — 46 evenings in a typical year. The wider season of sunsets at 7 PM or later lasts 201 days, from March 9 to September 25. At the other end of the year, sunsets before 4:30 PM begin around November 18 and last until January 1.
Days in Mercer Island first reach 12 hours of daylight around March 17, a few days before the March equinox, and drop back under 12 hours after September 24. Days with at least 15 hours of daylight run from May 12 to July 30. Days with less than 9 hours of daylight run from November 23 to January 17 (56 days).
The Sun's rising point moves along the horizon too. Around the June solstice it rises in the NE (53°) and sets in the NW (307°); by the December solstice it rises in the SE (125°) and sets in the SW (235°). That is a 72° swing — worth knowing when choosing a west-facing viewpoint for a summer sunset or an east-facing window for winter morning light.
Dates use the 2025 reference year. Clock-time milestones near daylight-saving changes move with the second Sunday in March and the first Sunday in November.
Daylight Through the Year in Mercer Island
Mercer Island lies at 47.57°N, high enough in latitude that residents feel the seasons clearly in the length of the day. Between the summer and winter solstice, daylight in Mercer Island changes by 7h 33m.
On the summer solstice around June 21, Mercer Island receives 15h 59m of daylight — the longest day of the year. By the winter solstice around December 21, that shrinks to 8h 26m, the shortest day. At the spring and autumn equinoxes, day and night are nearly equal at about 12h 11m, as they are everywhere on Earth.
Sunset moves fastest around September, when it shifts by up to 2.1 minutes a day in Mercer Island, and barely moves for weeks around the solstices. See how sunrise and sunset change through the year for why.
The Sun's Path Over Mercer Island
Where the Sun sits in the sky over Mercer Island depends on the season, and the contrast between summer and winter is set by the city's latitude of 47.57°N. On the summer solstice the midday Sun reaches 65.9° above the horizon in Mercer Island, its highest point of the year. On the winter solstice the midday Sun only reaches 19.0°, sitting much lower in the southern sky and casting long shadows even at noon.
Those roughly 47 degrees separating the summer and winter midday Sun are exactly what give Mercer Island its seasons.
The live sun path at the top of this page shows the Sun's altitude and compass bearing for the current moment or any chosen date.
Earliest and Latest Sunrises and Sunsets in Mercer Island
It is natural to assume Mercer Island sees its latest sunset on the longest day of the year, but it does not. The latest sunset actually falls around June 25 at about 9:11 PM, while the earliest sunset comes around December 10 at roughly 4:17 PM — noticeably before the December solstice.
On the morning side, the earliest sunrise in Mercer Island is around June 15 at 5:11 AM, and the latest sunrise around December 31 at 7:57 AM. The equation of time and daylight saving pull these dates away from the solstices — explained in why the latest sunset isn't on the longest day.
How Daylight Saving Time Moves Sunrise and Sunset in Mercer Island
Mercer Island, Washington changes its clocks twice a year, and both changes are visible in this page's numbers. On the second Sunday in March, Mercer Island springs forward and the evening changes overnight: sunset jumps from about 6:05 PM on Saturday to about 7:06 PM on Sunday. The price is paid at dawn — sunrise slips from around 6:35 AM back to 7:33 AM, so mornings turn dark again just as they were brightening.
The reverse comes on the first Sunday in November, when clocks fall back: sunset drops from about 5:51 PM to 4:49 PM in a single day — the abrupt start of the early-dusk season — while sunrise brightens from around 7:54 AM to 6:55 AM.
Only the clock label shifts on those Sundays; the times above are for a typical year. More in how daylight saving time changes sunrise and sunset.
Golden Hour & Blue Hour Photography in Mercer Island
For photographers in Mercer Island, Washington, the planner shows your selected date's morning and evening golden-hour and blue-hour windows. Choose Today, Tomorrow, or a date in the calendar; all clock times are calculated in Mercer Island's local timezone.
Golden "hour" is a misnomer — its length in Mercer Island depends on the season, because it lasts as long as the Sun takes to climb from the horizon to 6° (or descend back). Around the equinoxes it runs about 41 minutes; near the June solstice, when the Sun rises and sets at a shallower angle, it stretches to roughly 48 minutes, and near the December solstice it lasts about 53 minutes.
See the golden hour guide and blue hour guide for how to plan a shoot around these windows.
Solar Energy Potential in Mercer Island
Under clear skies, Mercer Island, Washington receives about 4.5 peak sun hours per day averaged across the year — from roughly 1.1 in December up to 8.1 in June. One peak sun hour equals one hour of sunlight at full intensity (1 kW/m²), the standard unit for estimating solar panel output.
Because Mercer Island sits at 47.6°N, a fixed, south-facing panel captures the most energy over the year when tilted at roughly 48° from horizontal — about equal to the latitude. If you adjust the tilt seasonally, flatten to about 33° in summer, when the Sun rides high, and steepen to about 63° in winter, when it stays low.
These are clear-sky upper bounds from Mercer Island's solar geometry, not a forecast; clouds, shading, and equipment lower real output. See what peak sun hours mean.
How Mercer Island Compares
Daylight in Mercer Island swings 7h 33m between the June and December solstices. The median across the 1,847 cities on this site is 5h 16m, so the seasons move the clock 2h 17m further in Mercer Island than in a typical American city. By that measure Mercer Island ranks 27th of 1,847 nationally, and 18th of the 52 Washington cities listed here — counting from the largest swing down.
Mercer Island sits about 2.2° west of 120°W — the meridian Pacific Time is built around. Longitude alone therefore puts mean solar noon roughly 9 minutes after clock noon in standard time, so the Sun runs behind the clock here, which is why evenings hold light later than the time zone would suggest. The equation of time then moves true solar noon up to about 16 minutes either side of that through the year.
About Sun Times in Mercer Island
Mercer Island, Washington, has an estimated urban-area population of 25,307. Its primary county or equivalent is King; its center is at 47.57°N, 122.23°W. Clocks here follow Pacific Time, which is the timezone all sunrise, sunset, golden-hour and twilight times on this page are shown in.
Times are computed for Mercer Island's city-center coordinates, so towns to the east see each event slightly earlier and towns to the west slightly later; the nearby-cities list above shows the typical gap.