After completing the main Omizu-tori (water-drawing ceremony) at Todaiji Temple in Nara yesterday, we are now eagerly awaiting the cherry blossoms to bloom. Predictions for this year’s cherry blossom bloom have become active online. Many places are expected to have cherry blossoms blooming either on par with or earlier than usual in 2024. It is predicted that cherry blossoms will bloom in Tokyo and Hiroshima on March 20th (Wednesday), the day of the spring equinox. On the 23rd, Fukuoka, Kochi, Nagoya, and others are expected to bloom, and on the 25th, Osaka is also expected to see blossoms. As April begins, the cherry blossom front will advance northward to the Tohoku and Hokuriku regions, reaching Hokkaido by late April, with blooms expected in Sapporo on the 23rd. By mid-May, the cherry blossom front will reach the northernmost tip of Hokkaido, and including colder regions, cherry blossoms will traverse Japan until early June. Cherry buds are formed in the summer preceding their blooming year. During autumn to winter, they enter a dormant state to survive through the year. They awaken from dormancy when temperatures sharply rise after receiving sufficient cold stimuli. This awakening is termed “dormancy breaking.” There’s a unique rule called the “600℃ Rule,” where the “Dormancy Breaking Day” is hypothetically set as February 1st, and by adding up daily maximum temperatures from there, days surpassing a cumulative temperature of 600℃ are considered as the predicted bloom days. Although this rule is specific to Tokyo, it apparently has a precision where the actual blooming date differs by no more than three days at most. Please try it in your own region as well.

昨日奈良東大寺のお水取り本行も終えて、いよいよ桜の開花を待つばかりになりました。今年の桜開花予想がネットでも盛んに出始めました。2024年の桜の開花は平年並か平年より早まるところが多く、いよいよ来週3月20日(水)の春分の日に東京と広島で桜が開花する予想です。23日には福岡や高知、名古屋などで、25日には大阪でも開花の見込みです。４月に入ると、桜前線は東北・北陸地方を北上し、4月下旬には北海道へ到達し、札幌では23日に開花すると予想されています。そして５月中旬には北海道の最北端に到達し、寒冷地を含めると６月上旬まで桜は日本を駆け巡るわけです。桜の花芽は、開花前年の夏にはできています。それが秋から冬にかけて、生長しないように休眠状態に入って年を越します。そして充分に低温刺激を受けた後に気温がぐっと高まった段階で休眠から目覚めます。これを「休眠打破（きゅうみんだは）」といいます。この「休眠打破の日」を２月１日と仮定して開花予想の起算点に設定し、そこから毎日の最高気温を足し算して“600℃を超えた日”を開花予想日だとする「600℃の法則」と言うユニークな法則があります。東京都に限った法則ですが、実際の開花日と最大でも3日しかずれていないという精度らしいです。皆さんの地域でも試してみて下さい。