JWA 2025 Spring Pollen Dispersion Forecast (Part 3)
~Cypress pollen levels are rising and nearing their peak, the pollen season has reached its halfway point~
Press Release
On March 25, 2025, Japan Weather Association (JWA) released its 2025 spring pollen dispersion forecasts at both the national and prefectural levels. The forecasts cover cedar and cypress pollen nation-wide, with the exception of Hokkaido where white birch pollen forecasts are provided instead.
1. Peak Period of Cedar and Cypress Pollen
Cedar pollen is expected to pass its peak in many areas by the end of March, while cypress pollen is likely to reach its peak across a wide region in early April.
Due to recurring cold conditions in March, the cedar pollen peak arrived 5 to 10 days later than usual in many areas. In Fukuoka and Hiroshima, the cedar pollen peak passed in mid-March, and it is expected to subside in many areas by the end of March.
Meanwhile, cypress pollen has begun dispersing in various parts of Kyushu and in areas stretching from Shikoku to Kanto Koshin, and the pollen concentration is increasing (as of March 24). Due to recent warm weather in late March, the start of cypress pollen dispersion is expected to be observed in many areas from Shikoku to Kanto Koshin by the end of the month. Cypress pollen is likely to reach its peak over a wide area in early April, with the peak period expected to last from about 5 days to 2 weeks. In Sendai, the cypress pollen concentration is expected to be low, with no clearly defined peak.
From mid-April and onwards, pollen dispersion will gradually subside. However, as in previous years, pollen is expected to continue being airborne in some areas through the Golden Week holidays in the beginning of May. On days with strong winds, pollen concentrations may increase. Even after the peak has passed, it is advisable to continue checking pollen and weather updates and take measures against pollen.
2. Start of Cedar Pollen Dispersion in 2025 (JWA observations)
According to observations by JWA, the start of cedar pollen dispersion this year was roughly the same as usual in Chiyoda Ward, Tokyo, but occurred 4 to 13 days later than usual in other areas. Compared to last year’s usual and/or early arrival of pollen dispersion, this year showed similar timing in Chiyoda Ward, Tokyo, while other areas were 1 to 3 weeks late. This delay is believed to be influenced by colder or near-average temperatures in February.
3. Start of White Birch Pollen Dispersion (Hokkaido)
White birch pollen in Hokkaido is expected to begin dispersing in mid-April. The timing of its dispersion tends to be earlier with higher spring temperatures (March to May). This March, the temperature in Hokkaido has been above average, and the temperatures in April and May are also predicted to be warmer than usual. As a result, the start of white birch pollen dispersion is likely to be earlier than usual.
Pollen Dispersal Forecast:
For more information on pollen dispersal forecast, follow the link below;
https://www.jwa.or.jp/english/service/seasonal-news-pollen-dispersal-forecast/
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Originally released in Japanese: 2025/3/25
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