Ragweed Pollen
WeedsThe most significant weed allergen in North America. A single plant can produce up to a billion pollen grains per season. Increasingly spreading in Europe.
In a typical year, Ragweed Pollen season runs August to October, peaking around September.
Where is Ragweed Pollen highest today?
Live ranking across the cities we track, from today's forecast. Updated daily.
| Locations | Level | Count |
|---|---|---|
| Lyon · France | X.HI | 537 grains/m³ |
| Sarajevo · Bosnia and Herzegovina | X.HI | 536 grains/m³ |
| Tirana · Albania | X.HI | 443 grains/m³ |
| Grenoble · France | X.HI | 400 grains/m³ |
| Geneva · Switzerland | X.HI | 382 grains/m³ |
| Skopje · North Macedonia | X.HI | 373 grains/m³ |
| Chișinău · Moldova | X.HI | 330 grains/m³ |
| Bratislava · Slovakia | X.HI | 329 grains/m³ |
| Belgrade · Serbia | X.HI | 323 grains/m³ |
| Montpellier · France | X.HI | 247 grains/m³ |
Ragweed Pollen season by country
Typical windows from our country pollen calendars; the weather shifts them earlier or later each year.
| Country | Season | Peak |
|---|---|---|
| Australia | Jan–May | Feb–Apr |
| Germany | Aug–Oct | Aug–Sep |
| Japan | Aug–Oct | Sep |
| United States | Aug–Nov | Sep |
About Ragweed Pollen
Common ragweed is a North American weed that has become the most troublesome late-summer allergen in a growing part of Europe, from the Rhône valley through northern Italy, Hungary, Croatia and the Balkans. It is also established in parts of East Asia. A single plant produces enormous amounts of very light pollen, and its major allergen, Amb a 1, provokes symptoms at low concentrations. Distant plants matter too: ragweed pollen is carried hundreds of kilometres on the wind.
In the northern hemisphere it flowers from late summer until the first frosts, peaking in late August and September. In eastern Australia, where the plant is also naturalised, shortening autumn days bring it into flower from around mid-March instead. That timing catches people who are otherwise clear of hay fever by then, and in ragweed regions it extends the allergy year into October. Mugwort and other members of the daisy family share some allergens with it, and a ragweed allergy is sometimes linked to reactions to melon or banana.