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Pollen and hay fever: season and precautions

April to August.

These are general seasonal patterns for the Nordic and Baltic region, not a live forecast. Always check the current local advisory — the weather service, health authority or water-quality notice — before you head out.

April to AugustActive season
Birch in April–May, grasses in June–July, mugwort in AugustWorst period

The risk

The northern pollen season is compressed and intense. Birch pollen in spring is a particularly powerful allergen across the Baltics and Nordics, followed by grass pollen in early summer and weed pollen later. For sensitive people it brings a blocked and runny nose, itchy eyes and sneezing, and it can trigger asthma.

How to stay safe

Check the daily pollen forecast and plan outdoor exertion for lower-count times, often after rain. Antihistamines and steroid nasal sprays work best when started before the season peaks rather than once symptoms are bad. Keep windows shut on high-pollen days, and shower and change clothes after being outside to wash pollen out of hair and off skin.

Good to know

People with asthma should keep their reliever inhaler close during their trigger season.

Other seasonal risks

Ticks (Lyme disease and TBE)

Ticks wait on grass and low vegetation in forests, meadows and gardens and attach to skin as you brush past.

April to October, whenever the ground is above about 5 °C

Mosquitoes

Mosquitoes breed in still water and are at their fiercest around bogs, lakes and wet forest, particularly in the long northern twilight.

May to September

Forest and wildfire risk

After a run of dry days the forest floor, heath and peat dry out and ignite easily.

May to August, during dry spells

Blue-green algae (cyanobacteria)

In warm, still water, cyanobacteria can multiply into a bloom that looks like spilled paint, greenish streaks or a scummy film on the surface.

July to August

Thin ice

Ice on lakes, rivers and the sea forms and melts unevenly.

The freeze of late autumn and the thaw of spring

Source: Seasonal patterns follow standard public-health and safety guidance for the region; confirm with the current local advisory. · checked 2026-09-04

Frequently asked questions

When is pollen and hay fever worst?

Birch in April–May, grasses in June–July, mugwort in August.

How do I reduce the risk from pollen and hay fever?

Check the daily pollen forecast and plan outdoor exertion for lower-count times, often after rain.

Enjoy the outdoors year round

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