Trends and Policy of Heat Illness in Japan
2/1 2025
Author: Naoko Hamashima
Japan has set late April to late October 2024 as the operational period of the “Heat Stroke Alert”. In particular, starting in 2024, a new “Special Heat Stroke Alert” will also be issued during this period as necessary, based on the revised Climate Change Adaptation Law. “Special Heat Stroke Alert” is issued when heat stress index of 35 or higher at all observation points in the prefecture. When a special alert is issued, the national government, local governments, businesses, and other entities will provide support so that each individual can practice maximum preventive actions as a principle of self-help, as well as mutual aid and public assistance. In addition, the government, local governments, businesses, and all other entities will provide support so that each individual can practice maximum preventive actions as mutual aid and public assistance. In addition, if the mayor of the municipality has designated heat shelters in advance, they will be open when the special heat stroke alert is announced. Fortunately, no Special Alert was issued in 2024, as there were no areas where the heat stress index reached the level that required the issuance of a Special Alert.
April-October 2024 saw many days with high temperatures throughout the country. In particular, the average temperature in summer (June-August) was the hottest in western Japan and Okinawa/Amami, and tied for the hottest in eastern Japan. Against this backdrop, the number of deaths due to heat stroke has been increasing every year. As shown in Chart 1, for example, the number of deaths from heat stroke has exceeded 1,000 every year since 2018, except for 2021.
The number of emergency medical evacuees is also on the rise, as shown in Chart 3. In particular, from May to September 2024, 97,578 people were transported due to heat stroke, the highest number since the survey began in 2008. 2024 was the second hottest month on record for June and July, and the hottest month on record for September, due to a prolonged period of extremely hot weather.
Table 1 shows the number of Heat Stroke Alert issued by regional forecasting areas. Numbers of issued in each area are shown in the leftmost column. The rightmost column shows the number of warnings issued divided by the number of observation sites, since the greater the number of observation sites, the greater the number of warnings issued. As can be seen from the table, the frequency of warnings issued in FY2024 tends to be higher in the Tokai region and westward.
As mentioned above, in 2024, no prefecture had a heat index of 35 or higher for all locations within the prefecture, and therefore no special alerts were issued. However, there were a total of 10 prefectures where the heat index at all locations was 33 or higher, so caution should be exercised in the future.
To prevent heat illness, Appropriate use of air conditioning, frequent intake of water and salt, and the close supervision and encouragement of those close to them are effective. It is especially important to install air conditioning in elementary and junior high schools, where physically weak children spend most of their time. According to data from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), public elementary, junior high and high schools are equipped with air-conditioning systems as shown in Chart 4.
Ratio of public elementary and junior high schools with air cooling system installed
The Ministry of the Environment is also disseminating information on heat stroke in English and other languages. When a special warning is issued, it is desirable to disseminate information on the English version of the Ministry of the Environment's website and on the English version of “X” for foreign tourists.
Heat Illness Prevention Information provided by MoE