What is tsuyu, and why does everyone talk about the weather so much in June?
From roughly early June to mid-July (varies by region), much of Japan enters tsuyu: weeks of high humidity and frequent rain. Shops sell dehumidifiers, mold sprays, and plastic umbrella-bag stands appear at entrances.
Tsuyu is a real meteorological season caused by a stationary rain front, and daily life—laundry, mold prevention, umbrella etiquette—reorganizes around the humidity.
Why — five layers
A stationary front (baiu front) sits over the archipelago as warm and cool air masses meet, producing prolonged rain and humidity.
The Meteorological Agency officially announces the start and end of tsuyu by region, so it functions as a recognized calendar season.
Because indoor drying, mold, and wet floors affect everyone, humidity-related habits (drying laundry indoors, wiping umbrellas) become shared courtesy.
International view
Monsoon seasons exist across Asia, but Japan's officially declared tsuyu, and the specific gear culture (quick-dry laundry, umbrella bags at every door), is distinctive.
But not always
Hokkaido essentially has no tsuyu, and some 'empty rainy seasons' (kara-tsuyu) bring little rain, so the experience varies widely by year and region.
What to do
Carry a compact umbrella daily in June–July, use the umbrella bags/racks at shop entrances, and air out or dehumidify closets to prevent mold on clothes and shoes.
Sources
- Japan Meteorological Agency tsuyu announcements
- baiu front meteorology