The Longest Day

Posted by Admin on 21 June 2006, 12:00 am

From Matt Rosenberg …

On or around June 21st each year, the rays of the sun will be perpendicular to the Tropic of Cancer at 23°30' North latitude. This day is the summer solstice in the Northern Hemisphere.

On this day, the earth's "circle of illumination" will be from the Arctic Circle on the far side of the earth (in relation to the sun) to the Antarctic Circle on the near side of the earth. The equator receives twelve hours of daylight, there are 24 hours of daylight at the North Pole and areas north of 66°30' N, and there are 24 hours of darkness at the South Pole and areas south of 66°30' S.

June 20th-21st is start of summer in the Northern Hemisphere but simultaneously the start of winter in the Southern Hemisphere. It's also the longest day of sunlight for places in the Northern Hemisphere and the shortest day for places south of the equator.

However, June 20th-21st is not the day when the sun rises earliest in the morning nor when it sets latest at night. As we'll see, the date of earliest sunrise or sunset varies from location to location.

We'll start our tour of the solstice in the USA in the north, with Anchorage, Alaska and head south in the U.S. and then move on to international cities. It's interesting to compare the difference in sunrise and sunset in various locales around the globe.

Anchorage, Alaska
On June 21st, the sun rises in Anchorage at 4:20 am and sets at 11:42 pm. The earliest sunrise Anchorage experiences is at 4:20 am but lasts from June 15th until June 23rd. The latest sunset also corresponds to the solstice sunset at 11:42 pm but lasts from June 21st until June 26th.

Seattle, Washington
The solstice in Seattle experiences a sunrise at 5:11 am and sunset at 9:10 pm. The earliest sunrise of 5:10 am lasts from June 13th-18th. The maximum sunset of 9:10 pm lasts from June 20th until July 2nd.

Portland, Oregon
Portland's solstice sunrise and sunset correspond precisely with its latest sunrise and sunset of 5:21 am and 9:03 pm. The maximums last from June 10th-21st and June 21st-July 2nd respectively.

New York City, New York
The Big Apple sees the sun rise at 5:24 am on June 21st and set at 8:30 pm. Maximums are one minute off – 5:23 am from June 12th-17th and 8:31 pm from June 22nd-July 3rd.

Sacramento, California
On June 21, Sacramento's sunrise is at 5:42 am and its sunset is at 8:33 pm. The maximums are each one minute off of the solstice times. The earliest sunrise in Sacramento is 5:41 am which lasts from June 7th-20th and the latest sunset is at 8:34 pm from June 25th-July 1st.

Los Angeles, California
What a difference 400 miles makes! When I was a boy growing up in Sacramento, I remember my grandmother calling from Los Angeles on the telephone late on summer nights. She'd be upset that I was still out playing even when it was dark. Explaining that the sun had still not set in Sacramento was an impossible proposition.

Nonetheless, on June 21st the sun rises in L.A. at 5:41 am and sets at 8:07 pm, which would've given me a full 26 extra minutes of sun-lit play time! L.A.'s earliest sunrise is the same as the solstice and lasts from June 4th-21st but the sunset is one minute later, 8:08 pm from June 28th-July 1st.

Miami, Florida
Miami experiences sunrise at 6:30 am on the 21st and sunset at 8:14 pm. Its maximums are 6:28 am from June 6th-12th and 8:16 pm from June 30th-July 5th.

Honolulu, Hawaii
Much closer to the equator and the 12-hour daylight that places on the equator experience on June 20th-21st, Honolulu has a sunrise of 5:50 am and sunset of 7:16 pm. The earliest sunrise in Hawaii is 5:49 am from May 28th-June 18th and the latest sunset is 7:18 pm from June 29th-July 10th.

Reykjavik, Iceland
Reykjavik lies at 64°9' North of the equator, just a few degrees south of the Arctic Circle (66°30'N) that experiences 24 hours of daylight on the summer solstice.

However, the 2:58 am early sunrise on June 21st in Iceland combined with a midnight sunset makes for a long period of daylight. The maximums for Reykjavik match the solstice sunrise and sunset but last from June 17th-23rd and June 20th-24th respectively.

London, United Kingdom
London's sunrise on June 21st is at 4:42 am and sunset is at 9:20 pm. Sunrise at 4:42 am is London's earliest, from June 11th-22nd but the sunset maximum is 9:21 pm from June 22nd-28th.

Tokyo, Japan
On June 21st, the sun rises in the land of the rising sun at 4:25 am and sets at 6:59 pm. Tokyo's earliest sunrise is 4:24 am from June 11th-14th and its latest sunset is at 7:00 pm from June 22nd to July 6th.

Mexico City, Mexico
Mexico City's sunrise on the solstice is 6:58 am and sunset is at 8:16 pm. Sunrise maximum for Mexico City is 6:56 am from May 31st-June 11th and sunset maximum is 8:18 pm from June 27th-July 14th.

Nairobi, Kenya
Nairobi, which is merely 1°17' south of the equator, has exactly 12 hours of sunlight on June 21st, the sun rises at 6:33 am and sets at 6:33 pm. It experiences its longest day on December 21st. On that day, sunrise is at 6:22 am and it sets at 6:37 pm.

Nairobi's earliest sunrise is from November 3rd-11th at 6:09 am and its latest sunset is at 6:51 pm from January 28th-February 18th! The lack of diversity in Nairobi's sunrise and sunset throughout the year provides a clear example of why lower latitudes don't need Daylight Saving Time – sunrise and sunset are almost at the same time year-round.

Matt Rosenberg is a professional geographer, university geography instructor, Red Cross volunteer, and the author of two books about geography.

After all these facts, just remember that, after June 28th, the nights are drawing in and Christmas is on the way!