Pollen & seasonal calendar
Tree, grass and weed pollen follow predictable seasonal patterns — but they are shifting with the climate. Know your region's season and plan before it starts.
How to read a pollen count
Counts are usually reported as low, moderate, high or very high, and reflect grains per cubic metre of air. Roughly: low affects only very sensitive people, moderate affects most people with that allergy, and high causes symptoms in nearly everyone sensitised — even with treatment. Our calendar shows typical monthly severity so you can plan weeks ahead.
Seasons at a glance
North America
Tree pollen from late winter into spring (earlier in the South), grass pollen late spring to mid-summer, and ragweed from August through October — the longest, most intense weed season in the world.
Europe
Birch trees dominate spring, grasses peak in May–July, and weeds such as mugwort follow in late summer. The Mediterranean runs longer and starts earlier; northern Europe is shorter and later.
Australia & NZ
Seasons run opposite to the Northern Hemisphere: tree pollen in spring (Aug–Oct), grasses into early summer, and summer weeds — a long grass season that drives much of the country's hay fever.
Seasons are shifting. Because of climate change, spring pollen now starts about 10–40 days earlier in many regions, seasons last roughly 20 days longer on average, and total pollen production is rising. Ragweed season at northern latitudes has extended by up to 27 days since 1995. Check local counts each season rather than trusting an old calendar.
Plan your season in five steps
- Find your allergensUse a skin prick or blood test to know what you react to.
- Learn your monthsNote when your allergens peak in your region (see the calendar above).
- Start medication earlyBegin your daily nasal spray about two weeks before the season.
- Time your outdoor lifePlan exercise and outdoor work around low-count days and hours.
- Review with a clinicianIf one season is miserable every year, immunotherapy is worth discussing.
Not sure if it's allergies?
A quick self-assessment with a personalised next-step plan.