Highest Sun of the Year
Just as day length depends on how far
you are from the equator, so does the sun’s height above the
horizon. As you move closer to the North Pole, daylight hours
increase, but the sun is also lower in the sky. On the other hand,
places closer to the equator — such as Honolulu or Miami — see
fewer daylight hours on the solstice, but the midday sun climbs
considerably higher in the sky.
In Washington, the sun reaches a
maximum height of 74.5 degrees above the horizon at solar noon on
June 21 (which is around 1:09 p.m.). According to time and date, the
sun is already higher in the sky at 8:30 a.m. than it is any time of
day on the winter solstice (Dec. 21).
Locations to our north see even more
daylight. In Boston, the sun is up for 15 hours and 17 minutes on the
solstice, while Seattle receives about 16 hours of daylight. And in
Fairbanks, Alaska, the sun is up for a whopping 21 hours and 50
minutes. Along and north of the Arctic Circle, the location of
sunrise and sunset starts to converge in the northern sky until
eventually the sun never sinks below the horizon. Instead, the sun
circles through the sky for 24 hours, a phenomenon commonly referred
to as the “midnight sun.”
One thing to remember is that while the
solstice is the longest day of the year, we don’t see our earliest
sunrise or latest sunset on June 21. Calculated down to the second,
the earliest sunrise in Washington was at 5:42 a.m. on June 13, while
the latest sunset occurs at nearly 8:38 p.m. on June 27. We can thank
Earth’s tilt and our elliptical orbit around the sun for this
astronomical quirk.
The reason we have solstices, and
seasons, is because Earth is tilted on its axis about 23.5 degrees.
This causes each hemisphere to receive different amounts of sunlight
throughout the year. In June, the Northern Hemisphere is at its
greatest tilt toward the sun, bringing us more direct sunlight and
warmer temperatures. It’s the opposite south of the equator, where
June 21 marks the first day of winter and the shortest day of the
year.
After June 21, the sun’s direct rays
will again begin to shift southward from the Tropic of Cancer toward
Earth’s equator. As a result, our long summer days will slowly get
shorter again, though the change won’t be noticeable for a few
weeks.
Between now and July 4, Washington
loses five minutes of daylight. A month from now, we’ll have 24
fewer minutes of daylight. And by Aug. 21, the sun will spend one
hour and 26 minutes less time above the horizon.
Even though we start losing a few
seconds of daylight this weekend, summer’s hottest days are still
upon us. Across much of the U.S. — and the Northern Hemisphere —
the hottest day of the year doesn’t usually arrive until July or
August.
The average high temperature in D.C. is
86 degrees on the solstice, but peaks at 89 degrees from July 7 to
22.
This delay, commonly referred to as
seasonal lag, happens because the amount of solar energy arriving at
the ground is greater than the amount leaving the Earth for several
weeks after the solstice. It’s largely driven by the oceans, which
take a lot longer than land to warm up and cool down, and release
heat slowly over time.
As we head past the solstice into the
final week of June, the extended forecast certainly appears summer
like. According to the latest outlook from the National Weather
Service’s Climate Prediction Center, above-normal temperatures are
likely for much of the Central and Eastern U.S. through early July.
Whatever the rest of summer brings, one
thing is guaranteed: After June 21, daylight begins to wane for the
next six months. So be sure to enjoy these long, bright evenings
before the nights get longer again.
On June 21, 2020 Sunday, the Sun will brighten our skies longer than on any other day in 2020. The summer solstice is here: our longest day and shortest night of the year, and the first day of astronomical summer in Earth's Northern Hemisphere. As a result, we may see the Sun takes its longest and highest path through the sky.
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