July 5, 2022

Summer is one of the four seasons, which is sandwiched between spring and autumn. Astronomically, from the summer solstice to the autumn equinox. The solar calendar refers to June to August, and the lunar calendar refers to April to June. It is the hottest period of about 3 months in the land with four seasons. In the northern hemisphere, the Gregorian calendar is around June-August, and in the southern hemisphere, it is around December-February.


There are several definitions for the summer period. The following is the definition in the Northern Hemisphere, which is off by half a year in the Southern Hemisphere.

Definition in Japan

The definition of "summer" in Japan is strongly influenced by the definition of "summer (xia)" in the Chinese calendar, and also has a complicated aspect due to the cultural influences of the West that accompany the Gregorian calendar in modern times. It is presented. During the pre-modern period, when they did not know the calendar system other than the Chinese calendar, the Japanese had to accept the definition of "summer (xia)" in the Chinese calendar as it was. However, in Japan, which has an oceanic climate and the sun is blocked by the rainy season during the summer solstice, the above-mentioned difference in daytime length and temperature is significantly larger than in China. In the Japanese archipelago, the peak temperature shifts to the time of the fall, so by the time the temperature peaks, the phenomenon that summer ends and autumn begins occurs. This gap is still the reason why the phrase "on the calendar ... summer (autumn) ... (the actual temperature is completely different)" is often used in weather forecasts. After entering the modern era and adopting the Gregorian calendar, this contradiction was freed from the premise. However, since Japanese people have been accustomed to the definition of the Chinese calendar for more than a thousand years, the arrival of the season is too late in the Western definition, and in Japan, the three months of June, July, and August are summer. It is common to say that there is. In Japan, this unique definition is also used in meteorology. The Japan Meteorological Agency calls a day with a maximum temperature of 25 ° C or higher a summer day (Natsubi) and a day with a maximum temperature of 30 ° C or higher a midsummer day (Manatsubi). The Japan Meteorological Agency has increased the number of days when the maximum temperature rises above 35 ° C due to the effects of global warming and the heat island. ) I decided to use the name. Except for the relatively cold Hokkaido and northern Tohoku, such days occur from June to September every year, mainly in July and August (depending on the year and region, they may occur even in May). The time will be in the summer range.

Definition in Europe, America and West Asia

In large areas from Western Asia to Western Europe and North America, the traditional definition is that summer refers to the period of one-quarter of the year from the summer solstice to the autumn equinox. This inherits the tradition of Western astrology established in the Mesopotamian civilization, and in Western astrology, the time when the sun passes the vernal equinox (sun ecliptic 0 degrees) is the beginning of spring, and this is celebrated as the New Year (exactly). According to the Sun Taiyin calendar, the day of the new moon near the spring equinox was set as the New Year. See the Jewish calendar). According to this idea, summer is the period from 90 degrees to 180 degrees ecliptic, that is, the period from the giant Cancer Palace to the Virgo Palace. The formal definition of "summer in the Northern Hemisphere" in modern astronomy also follows this. It is known that other ethnic groups in Western Europe, such as the Celts, seemed to have different calendars.

Definition in China

On the other hand, in Chinese civilization, summer (xià)