暑さ寒さも彼岸まで：2024年10月6日（日）

10月4日以降，朝と夜は，すっかりと秋めいてきた。日中の最高気温との温度差が大きくなり，体調管理が大変だ。その一方で，一日における気温水準の「ばらつき」の広がりは，不思議なことに，何か「トク」をした気分になる。実りの秋。紅葉も始まってきた。

　今年の夏を振り返ってみると，京都市では，先月の2024年9月20日に，今年の年間の猛暑日（一日の最高気温が35℃以上の日）の日数が54日を数え，観測史上最多となった。京都市は「夏は暑く，冬は寒い」ことでも有名であるが，特に，今年の夏は蒸して焦げるように暑かった。京都市のゲリラ豪雨の降り方をみると，もはや熱帯地方特有のスコールのようだ。自宅・大学間の自転車通勤途上の京都市堀川寺之内あたりで，何度となく，突如出現する20分程度のスコールに見舞われて，マンションの軒先をお借りして足止めを喰らったことか。

　また，京都市の熱帯夜（最低気温が25℃以上の夜）の日数は9月20日時点で61日を数えた。夜通しでエアコンを稼働させないと，熱中症になる恐れもあり，安心して寝ることもできなかった。京都市の真夏日（一日の最高気温が30℃以上の日）の年間の日数が，10月2日で101日目となった。統計開始以来の最長記録を更新しているということだ。大雑把に言うと，一年のうち4日に1日が真夏日という計算だ。

　今年の秋のお彼岸は，9月19日（木）の彼岸入りから9月25日（水）の彼岸明けまで，9月22日（日）は秋分のお中日（おちゅうにち）であった。秋分は二十四節気のひとつである。「暑さ寒さも彼岸まで」とあり，朝と夜は暑いながらも，秋の到来を思わせる涼しさも感じるようになった。特に，夜に鳴く虫の音は「季節の移り変わり」をまるで催促しているかのようだ。

　京都市の賀茂川（鴨川）河川敷の夜にマウンテンバイクを走らせていると，閻魔蟋蟀（エンマコオロギ）や松虫（マツムシ）などの鳴き声が聴こえてくる。平安時代の清少納言『枕草子』や紫式部『源氏物語』にもチンチロリンとなく松虫が登場していた。

Heat and cold last only until the equinox: Sunday, October 6, 2024

Since October 4, the mornings and evenings have completely taken on an autumn feel. The temperature difference between the daytime highs and lows has grown, making it challenging to manage my health. However, the increasing “variation” in temperatures throughout the day strangely gives me a sense of “gaining something.” It’s the season of harvest. The leaves have also started to change colors.

Looking back at this summer, in Kyoto City, on September 20, 2024, the number of extremely hot days (with a maximum daily temperature of 35°C or higher) reached 54, the most in recorded history. Kyoto City is famous for being “hot in the summer and cold in the winter,” but this summer was especially humid and scorchingly hot. The pattern of sudden downpours in Kyoto now resembles tropical rainstorms. On my bicycle commute between home and the university, I’ve often been caught by sudden 20-minute showers in the Horikawa Teranouchi area of Kyoto City, seeking shelter under the eaves of buildings to wait them out.

Additionally, as of September 20, the number of tropical nights (where the minimum temperature remains above 25°C) in Kyoto City had reached 61. Without running the air conditioner all night, there was a risk of heatstroke, and I couldn’t sleep peacefully. The number of hot summer days (with a maximum daily temperature of 30°C or higher) in Kyoto City hit its 101st day on October 2, setting a new record since data collection began. Roughly speaking, that means one out of every four days in a year is a hot summer day.

This year, the autumn equinox period lasted from Thursday, September 19 (the beginning of the equinox), to Wednesday, September 25 (the end of the equinox), with Sunday, September 22, marking the day of the autumn equinox. The autumn equinox is one of the 24 solar terms in the traditional calendar. The phrase “Heat and cold last until the equinox” suggests that while it was still hot in the mornings and evenings, there was also a hint of coolness that heralded the arrival of autumn. Especially, the chirping of insects at night seems to urge the “changing of the seasons.”

While riding my mountain bike at night along the banks of the Kamo River in Kyoto City, I can hear the sounds of crickets like the Enma cricket and pine cricket. Even in classical works from the Heian period, such as Sei Shonagon’s Makurano Soushi (The Pillow Book) and Murasaki Shikibu’s The Tale of Genji, pine crickets that chirp “chin-chiro-rin” made an appearance.