Japan Meteorological Agency Announces Early Rainy Season in Okinawa

The Japan Meteorological Agency announced that the rainy season began in the Okinawa region on May 4, 2026 ^[1].

This shift in weather patterns creates a sharp contrast across the archipelago, bringing heavy precipitation to the south while the Kanto region experiences an early surge of summer heat. The divergence highlights the volatility of spring weather transitions in Japan.

Officials said the rainy season in Okinawa arrived six days earlier than the climatological average ^[1]. A low-pressure front and an associated rain band triggered the early onset of the season ^[1].

Simultaneously, a warm front is pushing temperatures upward in the Kanto region, which includes Tokyo, Saitama, and Gunma ^[1]. Forecasts indicate that central Tokyo could reach 28 °C ^[1]. In the Kanto interior, cities such as Kumagaya, Chichibu, and Maebashi are expected to hit 30 °C ^[1].

While some reports suggest these temperatures will peak today, other data indicates the Kanto interior is more likely to approach the 30 °C threshold by May 11, 2026 ^[2].

Wind conditions are also fluctuating across the country. Maximum instantaneous wind speeds of approximately 25 m/s were observed in Yokohama and Chiba ^[1]. Higher speeds of approximately 30 m/s are expected in northern Japan ^[1].

This heat in Kanto follows the first nationwide summer-day of the year, which occurred on Hahajima island in Okinawa on May 1, 2026 ^[2]. That location recorded a temperature of 30.5 °C ^[3]. Some earlier reports suggested the first 30 °C reading in Okinawa occurred as early as April 1, 2026 ^[4].