Warm weather, swimming and vacations — such events often herald the arrival of summer. Most people mistakenly believe that the season starts with the dawn of the summer solstice, but there are actually two definitions of summer. Let's take a look at the hottest time of the year.
A matter of definition
Summer is the warmest season of the year, falling between spring and autumn. Temperatures over the period differ based upon the location on the Earth; regions near the equator are warmer than those lying near the poles.
Most people think of astronomical summer when they define the season. Astronomical summer runs from the summer solstice until the autumn equinox. The summer solstice is the day of the year in which the sun is up the longest, while the equinox occurs when night and day are approximately the same length. Seasons differ based on ones location on Earth. In the Northern Hemisphere, the summer solstice occurs between June 20 and 22 each year, when the North Pole is tilted at the greatest angle toward the sun. In the Southern Hemisphere, it occurs between December 20 and 23, when the South Pole is tilted toward the sun. [Image Gallery: Stunning Summer Solstice Photos]
However, you don't have to wait until the middle of June or December to feel changes in the weather. Meteorologists define summer as a three-month period of time; June, July and August north of the equator, and December, January and February to the south. During these months, temperatures tend to be higher than over the rest of the year.
Weather in the summer grows warmer, and in some areas, the heat translates to drier temperatures. This hot, dry time of year can lead to droughts, where water is in short supply. Heat waves, times of excessively hot weather that include spikes in temperature, can also occur. Both can create a number of problems for people and wildlife.
However, in many tropical regions, summer is the time of the "wet season," when the average annual rainfall is at its maximum. Vegetative growth increases during this time period. If winds are changing, the increased rainfall can also usher in monsoon season, a time of violent rainy storms.
Many summer deaths are caused by dehydration, especially during heat waves. While you should always seek to drink sixty-four ounces of water each day, consumption is especially important when temperatures soar. Similarly, be certain to practice water safety; never swim alone or while impaired.
The excessive temperatures and dry weather often associated with summer, as well as the violent monsoons, often causes rising death tolls. Let's take a look at a few instances of extreme summer weather:
London, 1858: Temperature wasn't the only unbearable problem for the city of London in the summer of 1858. Water closets had become the new rage, and much of the raw sewage made its way to the Thames River. When the heat spiked, the stench blanketed the city. But the noxious odor was only the beginning; many still drank from the river, and thousands died from diseases. In 1865, a newly designed sewer system helped prevent a repeat of the stinky summer.
Australia, 1923-1924: The town of Marble Bar in Western Australia set a world record when the 160 days between October 31, 1923, and April 7, 1924, reached temperatures above 100 degrees Fahrenheit (37.7 Celsius).
The Dust Bowl, 1930s: Coming on the tail end of the Great Depression, the 1930s saw several years of drought and dust storms across the central United States. The initial drought turned farmers' fields into dust that blew across the country, occasionally traveling all the way to the Atlantic Ocean. In 1936, heat waves added to discomfort, with Yuma, Arizona, experiencing 101 consistent days of temperatures over 100 degrees F (37.7 C).
Chicago Heat Wave of 1995: Approximately 700 people died in Chicago over the course of five days when the temperature hit 106 F (41 C) in July 1995. Excessive humidity caused temperatures to seem higher than 120. As more and more people cranked up the air conditioner, power grids reached their maximum capacity and burned out. This created even more problems for hospitals struggling with the increased patient load.
Europe, 2003: In July and August, rising temperatures in Europe claimed more than 70,000 lives. Temperatures climbed over 100 degrees, and were later determined to be higher than any summer since A.D. 1500. The high death toll makes this the most fatal heat wave in recorded history.
Russia, 2010: The world's second deadliest heat wave occurred only a few years later in Russia. With a high of 111 F (43.9 C), the excessive heat also sparked the worst drought in 130 years and fires across the country. Approximately 56,000 people died over the course of three weeks, many of them from drowning after swimming in unsafe locations or while intoxicated.