Yellow Sand (Kosa) in Japan: symptoms, season, and what travelers should do

Last updated: 2026-03-09

Yellow sand, or kosa, is one of the spring air-quality problems travelers often do not expect in Japan. The Japan Meteorological Agency (JMA) explains that aeolian dust consists of mineral particles lifted from semi-arid areas of the Asian continent and carried to Japan by westerly winds. In Japan, it is often observed from March to June, and it can make the sky look yellow or hazy. Heavy kosa can also reduce visibility.

What is yellow sand?

Yellow sand is not the same thing as pollen. Pollen comes from plants. Kosa is windblown mineral dust. JMA says it is monitored at meteorological stations and by satellite, and Japan also provides official analysis and prediction pages for it. That means travelers can check yellow sand conditions before a day of outdoor sightseeing (Learn more about why yellow sand happens and how it affects health).

Why travelers notice it

Many travelers first notice yellow sand as a hazy sky, lower visibility, or a day when their eyes, nose, throat, or chest feel worse than expected. This matters because spring in Japan is already the main pollen season in many areas. When yellow sand overlaps with pollen, some people feel much more uncomfortable outdoors.

Common symptoms

Japan’s Ministry of the Environment says yellow sand has been linked with itchy eyes, conjunctivitis, runny nose, sneezing, and skin symptoms. It also notes that yellow sand events have been associated with worsening of respiratory and circulatory diseases, and with increases in hospital visits and medical consultations in some studies. The same Ministry document says people who spend longer outdoors during yellow sand events may be more likely to develop symptoms.

If you already have allergies, asthma, or COPD

Yellow sand does not affect everyone in the same way. But if you already have cedar pollen allergy, asthma, or chronic respiratory problems, it deserves more caution. The Ministry of the Environment specifically notes that the timing of yellow sand can overlap with cedar pollen season, so people with cedar pollen allergy should be careful. Japan’s Allergy Portal also lists PM2.5 and yellow sand among factors that can worsen asthma.

What to do on bad yellow sand days

The most practical step is simple: check the official yellow sand forecast and reduce long outdoor exposure on bad days. This is especially sensible if you already know that spring air irritates your eyes, nose, or breathing. On hazy days, it may be smarter to move temple gardens, long park walks, or outdoor day trips to another day and choose more indoor activities instead. JMA publishes both monitoring and forecast pages for aeolian dust, so this is one of the easier seasonal risks to check in advance.

When to seek medical care in Japan

Do not treat it as “just spring discomfort” if you have wheezing, shortness of breath, chest tightness, worsening asthma, or a cough that is clearly getting worse. The evidence summarized by Japan’s Ministry of the Environment links yellow sand with worsening respiratory symptoms, and the Allergy Portal advises prompt medical attention when asthma symptoms become severe. If breathing is hard, speech is difficult, or symptoms are severe, seek urgent help.

Yellow sand vs pollen: which is worse?

They are different problems, but they can arrive in the same season. For many travelers, the real issue is not choosing one over the other. It is the overlap. Pollen may already be irritating your nose and eyes, and yellow sand can make the same day feel even worse. That is one reason spring in Japan can be more physically tiring than travelers expect, even when the temperature is pleasant.

Quick advice for travelers

If you are visiting Japan in March, April, or May, and you wake up to a hazy sky with worse-than-usual eye, nose, throat, or breathing symptoms, yellow sand is one possible reason. Check the official forecast, shorten outdoor exposure that day, and take your symptoms more seriously if you already have pollen allergy, asthma, or another respiratory condition.

FAQ

Is yellow sand common in Japan?

It is seasonal rather than constant. JMA says yellow sand is often observed in Japan from March to June.

Is yellow sand the same as pollen?

No. JMA describes yellow sand as mineral dust transported from semi-arid areas of the Asian continent, while pollen comes from plants. They can, however, overlap in spring and make symptoms feel worse.

Can yellow sand make allergies feel worse?

Yes, it can. Japan’s Ministry of the Environment says yellow sand has been linked with eye, nose, and skin symptoms, and it specifically warns that cedar pollen season and yellow sand season can overlap.

Where can I check the yellow sand forecast in Japan?

JMA provides official aeolian dust monitoring and prediction pages.

Official sources

Japan Meteorological Agency: aeolian dust overview and forecast pages.
Ministry of the Environment, Japan: yellow sand and health effects.
Allergy Portal Japan: asthma aggravating factors.