Tenki, Vol. 72, No. 4

(Tenki is the bulletin journal of the Meteorological Society of Japan in Japanese.)

TENKI, Vol. 72, No. 4, pp. 167-181, 2025

What Determines the Variations in the Number of Heatstroke Patients Transported to
Hospital by Ambulance in Kyoto City?
--Analysis of the Linkage between Meteorological Factors and the Number of Tourists--

By
Tetsuzo YASUNARI*1 and Sicheng HE*2

*1 Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8047, Japan
*2 Disaster Prevention Research Institute, Kyoto University (Present affiliation: Research Institute for Humanity and Nature)

(Received 6 August 2024; Accepted 23 December 2024)

Abstract

The number of heatstroke patients in Kyoto city during the warm season (May-September) over the past 13 years (2011-2023) was estimated using the number of people transported to hospital by ambulance. Daily, seasonal and interannual variations of these numbers were analyzed in relation to changes in meteorological factors and the number of tourists visiting Kyoto. The number of people transported during the midsummer period under the Ogasawara anticyclone increases rapidly: more than 5 persons/day at mean daily temperatures above 28ßC, more than 10 persons/day above 30ßC and more than 20 persons/day above 31ßC. The seasonal trends in the number of people transported to hospital show, in most of the years, two peaks of number in mid-July and early August. The peak in July well corresponds with the Gion Festival (of 17 July), which is held several days after the end of the rainy season in most years, and the peak in August corresponds with the period of seasonal maximum temperature. A machine-learning analysis (by XGBoost method) quantitatively confirmed that the July-peak becomes remarkably large when a very large number of tourists visited the Gion Festival under conditions of insufficient heat acclimatization due to the rapid rise of temperature immediately after the end of the rainy (Baiu/Meiyu) season.