Japan Pollen Calendar: What's in Season, Month by Month
It's September, and ragweed (butakusa), giant ragweed (ōbutakusa) and mugwort (yomogi) are usually at their peak in Japan. One more type is still in the air too: grasses (ine-ka).
These windows are what a typical year looks like; the weather nudges them earlier or later. For what's actually in the air today, check the live pollen count for Tokyo or find your city.
Trees
Trees rule the first half of the year. Sugi (Japanese cedar), the allergen behind kafunshō for some 40% of Japan, flies from late January in the warm southwest through April, and hinoki (Japanese cypress) follows about a month behind. In Hokkaidō, where sugi is essentially absent, birch takes its place in late spring.
| Species | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sugi (Japanese cedar) | in season | peak | peak | in season | ||||||||
| Hinoki (Japanese cypress) | peak | peak | in season | |||||||||
| Alder (hannoki) | in season | in season | peak | peak | in season | in season | ||||||
| Birch (shirakaba) | in season | peak | in season | |||||||||
| Oak (konara/kunugi) | peak | peak | in season |
Grasses
Grasses (ine-ka) take over in early summer. Kamogaya (orchard grass) and other meadow grasses along riverbanks and parks drive the main May–July flight, with a smaller late-summer tail. In Hokkaidō and cool uplands everything runs about a month later.
| Species | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Grasses (ine-ka) | in season | peak | peak | peak | in season | in season | in season | |||||
| Kamogaya (orchard grass) | peak | peak | in season | in season | ||||||||
| Timothy (oawagaeri) | in season | peak | peak | in season | ||||||||
| Ryegrass (hosomugi) | peak | peak | in season |
Weeds
Autumn belongs to the weeds. Butakusa (ragweed) and yomogi (mugwort) fly from mid-August into October, peaking in September. They are the classic cause of autumn hay fever on roadsides and riverbanks across Japan.
| Species | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ragweed (butakusa) | in season | peak | in season | |||||||||
| Giant ragweed (ōbutakusa) | peak | peak | in season | |||||||||
| Mugwort (yomogi) | in season | peak | in season | |||||||||
| Plantain (heraōbako) | in season | peak | peak | in season | in season |
When does pollen season start and end in Japan?
Japan’s pollen year effectively starts in late January, when the first sugi (Japanese cedar) flights reach Kyūshū and the warm Pacific coast. The main sugi season runs February to April, moving southwest to northeast. Hinoki (Japanese cypress) follows about a month behind and peaks from late March to mid-April; many people are sensitive to both, so spring can feel like one continuous February-to-May stretch. Grasses carry early summer (May to July), and the autumn weeds, ragweed and mugwort, finish the year from mid-August to October. November and December are usually the quietest months. The map matters in Japan more than almost anywhere. Hokkaidō has essentially no sugi or hinoki: its spring problem is birch (shirakaba), from late April to June. Okinawa is largely free of both, and the far south starts several weeks before Tōhoku. These windows show a typical year nationally; for what’s actually in the air today, check the live forecast for Tokyo or find your city.
What about kanamugura, pine and rice?
A few pollens people ask about aren’t separate rows here. Kanamugura (Japanese hop) is one of Japan’s four canonical autumn allergens, flying from August to October along fences and riverbanks, especially in Kantō, but it isn’t yet one of the species our forecast model tracks individually. The visible yellow dust from pine (matsu) in April to June looks alarming but is only weakly allergenic; if your symptoms spike then, sugi, hinoki or grasses are the more likely culprits. Rice (ine) flowers briefly in August and is covered within the overall grasses row. A few rows use the closest tracked species for a Japanese native (alder for hannoki, birch for shirakaba, oak for konara and kunugi, mugwort for yomogi), with the season windows set for the Japanese species.
Frequently asked questions
When does sugi (Japanese cedar) pollen season end?
The main sugi season runs February to April, peaking from late February through March. It ends by late April in most of Japan, with hinoki (Japanese cypress) continuing into May.
When is hinoki pollen season in Japan?
Hinoki (Japanese cypress) season runs March to May, about a month behind sugi, peaking from late March to mid-April. It is heaviest in western Japan.
Why do I get hay fever in Japan in autumn?
Autumn hay fever in Japan is usually ragweed (butakusa), mugwort (yomogi) or Japanese hop (kanamugura), which fly from mid-August to October with a September peak, plus a late tail of grass pollen.