Japan expects mostly sunny weather across the archipelago on Saturday, May 16, 2025, as a mobile high-pressure system covers the region [1, 2].

The forecast indicates a significant rise in temperatures, signaling an early arrival of summer-like heat for several prefectures. This shift requires residents to prepare for high temperatures and protect themselves against strong UV radiation [1, 2].

According to TBS NEWS DIG, the high-pressure system is suppressing cloud formation, which will keep skies clear for most of the country [1, 2]. While the majority of the nation will experience clear weather, isolated rain is expected in Okinawa during the morning and in northern Hokkaido during the evening [1, 2].

Temperatures are expected to climb sharply in multiple locations. Saga is forecast to reach a maximum temperature of 31°C [1], while Morioka is expected to hit 30°C [1]. Other areas, including Osaka and Hiroshima, are also expected to experience "manatsubi," a Japanese term for days where temperatures reach or exceed 30°C [1].

In other major cities, the heat will be more moderate. Tokyo is forecast to reach a maximum of 26°C [1], and Sapporo is expected to hit 23°C [1].

Meteorologist Ryuichi Yonezu said the conditions are clear and ideal for outings, and that it will be refreshingly sunny and perfect for leisure [2]. TBS NEWS DIG said the high-pressure system is expected to cover the region, including northern Japan [2].

“"It will be refreshingly sunny and perfect for leisure"”

The occurrence of 'manatsubi' temperatures in mid-May suggests an accelerated transition into summer. When high-pressure systems stabilize early in the season, it often leads to prolonged periods of intense UV exposure and heat stress, potentially impacting agricultural planning and public health infrastructure before the official summer peak.