When does the pollen season start here?

Alder and hazel from late February in mild years, birch through April and May, grass from mid-May to July, mugwort in July and August. The three allergy waves arrive in that order every year.

When should I take vitamin D?

North of about 52°N the skin cannot make vitamin D roughly October to March — the supplement window, for those who take one. Best practice is a late-winter blood test first, then the national guidance dose; the month pages mark the transitions.

Ticks are active whenever it is above about +5 °C, with two peaks: May-June and September. The check after forest and tall-grass visits runs from April to October.

October to March, peaking in the depth of winter. The vaccine is best taken in October or November, before the peak.

TempoLife › Features › Health calendar by month

The health calendar

Twelve pages, one per month: daylight and vitamin D, seasonal produce, pollen, tick and flu season, and the health task of the month — written for the north (Estonia, Finland, Latvia).

12months

3 (alder/hazel · birch · grass · mugwort)pollen waves

Oct-Marvitamin D window

Apr-Oct, peaks May-Jun & Septick season

Month	Daylight	Pollen	The health task
January	6-7.5 h	None — pollen season is months away.	The vitamin D trough: if you take D in winter, this is the month to have started. The dark months are the test of the sleep routine — daylight anchors the body clock, and January is when the missing morning light shows up as sluggishness. Get outside around midday, keep the gym routine as the antidepressant it is.
February	7.5-9.5 h	None yet — but late February can bring the first alder and hazel pollen in mild years.	The last dark month, and the month seasonal mood is at its worst. The turnaround is measurable: by late February the days gain five minutes a day. Plan the spring restart now — shoes, routes, the first outdoor sessions — so March does not catch you unfit.
March	9.5-12 h	Alder and hazel pollen — the first allergy month for many.	Daylight returns to normal range — vitamin D skin synthesis resumes by late March. Allergy season starts: if alder and hazel are your triggers, the antihistamine habit starts now. The roads clear; walking and running move back outside.
April	12-15 h	Birch pollen — the big one. Alder and hazel continue.	Birch pollen month: the worst allergy weeks of the year for the largest group. Start the allergy routine before the peak if you know you react. Tick season opens — the checks after every forest or tall-grass visit start now. Outdoor training returns properly.
May	15-17 h	Birch peak early in the month, grass pollen from mid-May.	The best training month of the year: long light, moderate temperatures, everything outdoors. Tick risk is at its peak — repellent, tucked clothing in tall grass, and the evening check. Grass pollen starts: exercise early or after rain when counts are lowest.
June	17-18.5 h	Grass pollen peak — the second allergy wave.	Midsummer month: the light maximum and the sleep challenge it brings — bright nights suppress melatonin, and sleep shortens unless the bedroom is dark. Grass pollen peaks; the evening counts are the trick. Vitamin D from the sun is now abundant with modest exposure.
July	16.5-18 h	Grass pollen tails off; mugwort arrives late in the month.	Holiday month: heat days arrive, and hydration becomes the visible habit. The berries are the cheapest supplements of the year — eat them fresh by the punnet. Training in heat: mornings or evenings, lighter sessions, and the salt balance matters on long hot days.
August	14.5-16.5 h	Mugwort pollen — the late-summer allergy wave.	The season's end is visible: evenings shorten and the body starts banking light. The second tick peak arrives with the mushroom season — the foraging habit and the tick check go together. Allergy sufferers meet mugwort, the third wave.
September	12-14.5 h	Mugwort continues; the season ends this month.	The autumn transition: light falls fast, and the body clock shifts with it. This is the month to set the winter routine — fixed bedtime, the indoor training plan, the vitamin D start for those who take it. The first respiratory infections of the season circulate in schools and offices.
October	9.5-12 h	Pollen season over.	Vitamin D skin synthesis ends this month for the north — the supplement window opens for those who take one. The flu vaccination season starts; the time to take it is now, before the peak. Daylight falls below the threshold that matters for morning mood: the midday walk becomes the daily dose.
November	7-9.5 h	None.	The hardest month: the light is nearly gone, the flu season is building, and the winter mood settles in. The routine set in September is what carries November — fixed sleep, indoor training, the midday light dose, vitamin D in hand. Hand hygiene and sleep are the two infection defences that actually work.
December	6-7 h	None.	The darkest month, and the social one: the gatherings that carry norovirus and flu, the alcohol that fragments sleep, and the shortest days of the year. The health play is defence — sleep protected, alcohol modest, hands washed — not abstinence from the season. The solstice passes; the light returns.

The shape of the year

The northern year has a rhythm the body follows whether or not the calendar does: light climbs from January to June and falls back, vitamin D follows the sun angle, and the risk seasons — pollen, ticks, flu — take turns. Most of the year's health decisions have a month when they are cheap and a month when they are expensive: the flu shot in October costs nothing in December terms, and the sleep routine fixed in September carries the winter. The month pages exist to put those decisions on the calendar.

Sources: Finnish Meteorological Institute — seasons and daylight · University of Turku Aerobiology Unit — Finnish pollen season calendar · ECDC — seasonal influenza · Terviseamet (Estonian Health Board) — tick-borne disease guidance · checked 2026-09-07