Summer Begins 106 pm June 21



Summer Begins June 21


Frederick Kruse
and
Jonathan Finch



Summer begins at 106 pm CDT June 21 and ends September 23.  This is when the sun is the highest in the sky in the northern Hemisphere, which is referred to as the summer solstice. The sun rises further north and sets further north than at any other time of the year. The sun is directly overhead at 23 degrees north latitude (Tropic of Cancer) at 106 pm on June 21. The first day of summer marks the longest day of the year. This amounts to 14 hours and 47 minutes of daylight and 9 hours and 13 minutes of darkness at Dodge City.

However, if we use the climatological warmest period for our definition of summer, then the start and end of summer would both be earlier. The warmest 3-month period for Dodge City would start on June 7 and end on September 7. During this period, the average daily high (1971 to 2000) is at or above 85F. The warmest day on average for the 30-year period is July 24 (94F). Note that there is a 33-day lag at Dodge City between the longest day of the year (June 21) and the climatological warmest day (July 24).  To understand this, put a pan on the stove and turn the stove on high. The pan gradually warms and not all of a sudden. When the stove is turned off, the pan remains hot for awhile.

All materials have a lag time depending on their chemical composition. The lag time is longer for the oceans because water takes longer to warm up and cool down than land. The warmest water temperatures in the Gulf of Mexico are in September. This helps explain why hurricanes are more common during September when the land masses have already begun to cool off but the oceans are reaching their warmest temperatures.

For further information on sunrise/sunset times, moonrise/moonset, twilight and other astronomical data see the U.S. Naval Observatory web site.


Credits: Wilkimedia Commons (online), U. S. Naval Observatory




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