Western Japan entered the rainy season on June 4 [1].

The arrival of the rainy season brings increased humidity, which accelerates mold growth in homes and necessitates specific ventilation strategies to maintain hygiene.

Caster Takahiro Inoue said that the rainy season began on June 4 in the northern Kyushu, Chugoku, and Kinki regions [1]. Forecaster Aimi Sakaguchi said she expects the Kanto-Koshin region to enter its rainy season on June 7 or 8 [2].

Historical data provides a baseline for these expectations. The average date for the rainy season to begin in Tokyo is June 7 [1]. In Nagoya, the average start date is June 6 [1], while Niigata typically sees the season begin on June 11 [1].

As humidity rises, experts are addressing the common habit of leaving bathroom doors open after a shower to dry the room. A former housekeeper said that leaving the door wide open can be counterproductive. According to the expert, this habit can actually make the bathroom harder to dry and spreads moisture throughout the rest of the house [3].

However, guidance on bathroom ventilation remains contradictory among sources. While some experts advise against leaving doors fully open to prevent moisture from migrating into other rooms, other reports suggest that keeping the door open while the ventilation fan is running is the most effective way to let humidity escape [3].

Proper management of these spaces is critical during the June humidity peaks to prevent permanent damage to home interiors and protect resident health from mold spores.

“Western Japan entered the rainy season on June 4.”

The intersection of seasonal weather patterns and home maintenance highlights a common tension in urban living. While the rainy season is a predictable annual event in Japan, the conflicting advice on bathroom ventilation suggests that the 'correct' method may depend on the specific airflow and ventilation system of an individual home rather than a universal rule.