Patrick Skach's Blog

The Summer Solstice date of 2008 is Friday, June 20th beginning at 6:59pm.

A Summer Solstice Date of June 20th has not occurred since 1896 or 112 years ago.

Solstices occur twice per year when the tilt of the Earth's Axis is the furthest distance away from the Sun.   The Summer Solstice occurs on either June 20th, 21st or 22nd of each year and it marks the first day of the Astronomical Season of Summer. On the day the Summer Solstice falls, the Sun is farthest North or highest appearing in the sky.  It is also one of the days which have the Longest Hours of Daylight and the Shortest Hours of Darkness.  

 Notice the Sunlit portion of the Earth in the Northern Hemisphere from the Equator up to the Arctic Circle North Pole).  

The Winter Solstice occurs on either December 20th, 21st or 22nd of each year and it marks the first day of the Astronomical Season of Winter.  On the Day the Winter Solstice falls, the Sun is farthest South or Lowest appearing in the sky.  It is also one of the days which have the Shortest Hours of Daylight and the Longest Hours of Darkness.   Notice the Sunlit portion of the Earth in the Southern Hemisphere from the Equator down to the Antarctic Circle (South Pole).

  Below are some very informative website links which explain the Solstice in detail:

Here is an easy to understand guide explaining the Summer Solstice.  It includes a Beginner - Intermediate - Advanced tab and is also available in Spanish.
The Summer Solstice 
 
This animation displays the Earth's rotation in relation to the Sun throughout the Solstice and Equinox periods of the year.  Use the toolbar along the calendar bar to control the animation.   Choose the "Earth Profile Tab" for specific details as you view the animation.
 Earth - Sun Relations
 
This page contains a simple animation of where and when the sunlight shines upon the Earth and produces for us what we know as Day and Night. Read through the entire page to learn more about the Earth's Seasons, Equinoxes and Solstices.  Many more links included.
 24 Hour Time Lapse Animation
 
This animation is controlled by the viewer, yourself.  You can choose any specific day of the year to display the amount of daylight shining on the Earth in comparison to darkness.
 Length of Earth's Days & Nights
 
This page offers a very simple explanation of why we experience Seasons throughout the year due to the Earth's rotation in relation to the Sun.
Day vs Night Shadow
 
 
This animation shows how the length of daily light and dark periods change over the course of 1 year.
Antarctica Seasonal Cycle
 
 
If you would like to know exactly when a Summer Solstice or Winter Equinox will occur for any specific year, this chart provides the dates and time.
Astronomical Information Center
 
 
This is an animated explanation specifically for the Summer Solstice.
Summer Solstice Animation 
 
This is a Day-Night Earth View map which displays a comparison of the Earth which is Dark or Light at any given time.  Selection options are available below the map.
Earth Viewer

Before Sunrise and After Sunset there are intervals of time which there is Natural Light provided by the Atmosephere which does not receive Direct Sunlight. This period of time is know as Twilight. Twilight Definitions 

Now that we have an understanding of the Solstice & Equinox periods, let us examine some Sunrise & Sunset Dates & Times for 2008.                                      

                                      March           June            September         December

Sunrise:                       6:54am        5:16am       6:39am               7:16am

Sunset:                        6:04pm        8:31pm       5:48pm
  4:24pm

     

Hours of Daylight:      11:10           15:47           11:09                     8:08

Hours of Darkness:  12:50              8:13           12:51                   15:52  

As shown above, June 20th has 7 Hours & 39 Minutes of Additional Daylight Hours in comparison to this coming Winter Solstice which will occur on December 21st which will only have 8 Hours and 8 Minutes.  

Since the June Summer Solstice is typically considered a Summertime Benchmark of sorts, this would be an ideal time to examine Chicago's Daily Maximum Temperatures so far.  

Below is an Examination & Comparison Study of 70º and Higher Daily Maximum Temperatures in Chicago during the period from January 1st up to and including the June Summer Solstice Day over the past 138 Years (1871 - 2008)  

The Number of Days the Daily Maximum Temperature Reached 70º or Higher during the period of January 1st thru the Summer Solstice over the past 137 Years (1871 - 2007)

0 - 19 Days                                 3 Times                               2%

20 - 29 Days                             39 Times                             29%

30 - 39 Days                             47 Times                             34% <-- 2008  39 Days

40 - 49 Days                             41 Times                             30%

50 or More Days                         7 Times                               5%

Totals:                                     137 Times                            100%  

Now a Breakdown and Comparison of 2008                          

                     70º or Greater Daily Temperatures in 2008                        

                          70ºs      80ºs      90ºs      100ºs      Total

April:                   7            1          0            0                 8

May:                  10            2          0            0              12

June:                  7          11          1            0              19

Totals:              24         14          1            0              39

137 Year Avg:  20         13          3           0               36  

Here is what the Study above is telling us: So far, in 2008 (up to and including the June Solstice) Chicago has experienced 39 Days of Temperatures reaching 70º or Higher which falls into the most common Category of 30 - 39 Days.  

Also, for the same Time Period of January 1st thru June 20th Chicago's 39 Days of 70º or Higher Temperatures has surpassed the 137 Average of 36 Days by 3 Days.   

Most 70º & Higher Days                Least 70º & Higher Days

58 Days   in   1955                         18 Days    in    1882

58 Days   in   1977                         19 Days    in    1878

52 Days   in   1959                         19 Days    in    1924

52 Days   in   1987                         22 Days    in    1883

52 Days   in   1991                         22 Days    in    1892

51 Days   in   2007                         22 Days    in    1909

50 Days   in   1963                         22 Days    in    1935

49 Days   in   2005                         23 Days    in    1900

48 Days   in   1896                         23 Days    in    1901

48 Days   in   1934                         23 Days    in    1904  

The 137 Year Average is 36 Days 2008 Has Experienced   39 Days

Days Examined for Most & Least Above are January 1st thru the June Solstice of Each Year  

 

Earliest June Solstice: June 20th which has occurred   3   2% Times in 138 Years.

Typical June Solstice:  June 21st which has occurred  99 72% Times in 138 Years.

Latest June Solstice: June 22nd which has occurred  36 26% Times 138 Years                                                 

                                                       
                     Total:         138 100%