Summers in Japan are typically hot and rainy. Unlike much of the US, where warmer temperatures generally lead to less rain, Japan’s climate is heavily influenced by its surrounding oceans. Warmer air, driven by ocean currents, can carry more moisture, leading to more rain and warmer temperatures.
This beautiful pair of maps from Kenneth Wong demonstrates this relationship. They use data from the Japan Aerospace Exploration Agency (JAXA) to explore nighttime temperatures and rainfall rates in August 2024.
Ignited Night shows how nighttime land surface temperatures in August 2024 compare to recent years. It uses a red-to-blue color ramp to show deviations from average August temperatures from 2019 to 2023. Areas in red were warmer than normal, while areas in blue had lower temperatures.
The southeastern parts of the country, specifically the Kyushu and Okinawa, Chugoku, and Shikoku regions, all experienced warmer temperatures. You can also see elevated temperatures near Nagoya and Tokyo. Temperatures were lower near Kanazawa and in parts of the Kansai region.
Higher nighttime temperatures are one consequence of climate change. Over the past ten years, the number of nights with minimum temperatures above 25°C (77°F) has increased by a week or more in Japan.
Blue Rain maps the average precipitation rate in millimeters per hour for August 2024. Larger, darker blue circles represent higher rates of rain. Areas with lighter colors saw less rain.
Southern parts of the Kansai and Chubu regions saw some of the highest rain rates in August 2024. Parts of the Shikoku and Kyushu and Okinawa regions also experienced more rain. Conversely, the Chukogu region and parts of the Chubu and Kansai regions saw little to no rain. Across Japan, areas bordering the Sea of Japan saw less rain than the southern-facing coasts of the country.
When viewed together, the maps show that the places with the most rain also had warmer nighttime temperatures. And many places with the least amount of rain also had lower relative temperatures. Wong himself noted the stifling heat during nighttime walks during a trip to Japan. In extreme situations, these kinds of conditions can become dangerous. This phenomenon is known as the wet-bulb effect. The combination of both high temperatures and humidity can compromise the body’s ability to cool itself.
