summer in Tokyo One of the most popular topics in summer is ‘Is it getting hot in summer compared to the old days?’ According to the Japan Meteorological Agency, the temperature in Japan is steadily increasing in these 100 years and it’s obvious especially in Tokyo and other large cities. Compared with 100 years ago, the average temperature in Tokyo rose by 3.2 degrees. The highest temperature is picked up often but there’s a more serious problem in winter. In other words, the rate of increase in lowest temperature is larger than highest temperature. How and when the heat of summer has been changed? There is a heat map which shows the average daily temperature in Tokyo between June to September for these 140 years. The map shows that in 1920s it started to get warmer and warmer in Tokyo and the trend got obvious during the period of high economic growth between 1960 and 1980. Since 1990s, it’s not rare that the maximum temperature exceeds 30 degrees in July. On the other hand, 1993 is known as a cold summer. In 2010, it was the record-hot summer. Also, the temperature is increasing and at the same time the duration of the peak of heat is getting longer. Especially since the late 2000s, the average temperature exceeds 30 degrees in some days even in September. Although the average temperature changes every summer, it’s no doubt that it’s getting severe. It’s important we exercise caution more.