JWA 2025 Spring Pollen Dispersion Forecast (Part 4)
~Cedar and Cypress Pollen Season to End, Osaka Records Highest Pollen Concentration in the Past Decade (Preliminary Values) ~
Press Release
On March 25, 2025, Japan Weather Association (JWA) released its 2025 spring pollen dispersion forecasts at both 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. This is the last spring pollen dispersion forecast for 2025.
1.Cedar and Cypress Pollen Dispersion to End Soon
The cedar and cypress pollen season is coming to an end from Kyushu to Tohoku from mid-April. In Kyushu, the peak season of cypress pollen has almost ended by early April, while in the wide area from Chugoku and Shikoku to Tohoku, the cedar and cypress pollen peak is expected to end by mid-April. However, there are likely to be days with slight pollen dispersion in various regions until around early May. Particularly on windy days, pollen dispersion tends to increase, so it is advisable for those who are sensitive to pollen to take precautions for a little while longer.
2.Pollen Dispersion Status of Cedar and Cypress in Chiyoda Ward, Tokyo (JWA Observation)
According to JWA observation, in Chiyoda Ward, Tokyo, cedar pollen began to disperse on February 15th this year. Although it was followed by a period of approximately 10 days of low pollen dispersion, cedar pollen dispersion increased at the end of February, when springlike warmth set in, and entered its peak period. Additionally, cypress pollen began to disperse on March 19th, and in late March, the peaks of cedar and cypress coincided, resulting in extremely high pollen concentrations observed for nearly a week. Cedar pollen reached its peak at the end of March, and due to frequent rainy days until mid-April, cypress pollen dispersion was suppressed, ending its peak in mid-April.
The graph shows the cumulative pollen observed per square centimeter in Chiyoda Ward, Tokyo, and it compares the past three years (2024, 2023, and 2022). This year (orange), the pace of increase in the cumulative pollen concentration is slower compared to 2024 (dark green) and 2023 (green). It has progressed similarly to 2022 (light green), which had low temperatures in February. This year’s pollen dispersion is expected to end soon, with the total pollen concentration being similar to 2022, slightly less than the usual years.
3.Preliminary Values of Cedar and Cypress Pollen Concentration (in Osaka and Tokyo as of April 15th)
According to JWA observation, the cumulative pollen concentration of cedar and cypress as of April 15th this year in Osaka was 2.3 times higher than usual and 5.1 times higher than last year (2024), reaching an extremely high level – the highest in the past 10 years. In Chiyoda Ward, Tokyo, it was about 30% less than the usual years and last year.
The graph shows the cumulative pollen concentrations in Osaka City and Chiyoda Ward, in Tokyo, over the past 10 years and this year (as of April 15).
4.White Birch Pollen Dispersion Forecast for Spring 2025 (Hokkaido)
White birch pollen in Hokkaido is expected to begin dispersing in late April over many areas, including Sapporo, and continue through May. During the long holiday, many areas are likely to experience significant dispersion. In this season, pollen concentration of white birch is expected to be slightly higher than usual. However, since last season’s concentration was extremely high, it is expected to be lower in comparison.
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: 2025/4/18
PDF DOWNLOAD：2025 Spring Pollen Dispersion Forecast Part4
