Pollen calendar for Ireland
When each pollen is in the air, month by month, and what this year’s season looked like in every county.
Month by month
| Type | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Hazel | January: In the air | February: Peak | March: In the air | April: none | May: none | June: none | July: none | August: none | September: none | October: none | November: none | December: none |
| Alder | January: none | February: In the air | March: Peak | April: In the air | May: none | June: none | July: none | August: none | September: none | October: none | November: none | December: none |
| Willow | January: none | February: none | March: In the air | April: Peak | May: none | June: none | July: none | August: none | September: none | October: none | November: none | December: none |
| Ash | January: none | February: none | March: In the air | April: Peak | May: In the air | June: none | July: none | August: none | September: none | October: none | November: none | December: none |
| Birch | January: none | February: none | March: none | April: Peak | May: In the air | June: none | July: none | August: none | September: none | October: none | November: none | December: none |
| Oak | January: none | February: none | March: none | April: In the air | May: Peak | June: In the air | July: none | August: none | September: none | October: none | November: none | December: none |
| Grass | January: none | February: none | March: none | April: none | May: In the air | June: Peak | July: Peak | August: In the air | September: none | October: none | November: none | December: none |
| Plantain | January: none | February: none | March: none | April: none | May: In the air | June: In the air | July: In the air | August: In the air | September: none | October: none | November: none | December: none |
| Nettle | January: none | February: none | March: none | April: none | May: none | June: In the air | July: Peak | August: Peak | September: In the air | October: none | November: none | December: none |
| Mugwort | January: none | February: none | March: none | April: none | May: none | June: none | July: In the air | August: Peak | September: In the air | October: none | November: none | December: none |
| Mould spores | January: none | February: none | March: none | April: none | May: none | June: In the air | July: Peak | August: Peak | September: Peak | October: In the air | November: none | December: none |
- In the air
- Peak
- This month
Typical timing in Ireland. Each year shifts by a week or two with the weather: a warm spring brings trees forward, and a wet June holds grass back.
The 2026 season, week by week
Tree pollen ran from early March to the end of April, then a quiet May, then grass from early June to early August. The worst day was 25 June, when every county was High.
| Week of | Counties High |
|---|---|
| 23 Feb | 0% |
| 2 Mar | 0% |
| 9 Mar | 0% |
| 16 Mar | 3% |
| 23 Mar | 0% |
| 30 Mar | 0% |
| 6 Apr | 4% |
| 13 Apr | 1% |
| 20 Apr | 30% |
| 27 Apr | 0% |
| 4 May | 0% |
| 11 May | 0% |
| 18 May | 0% |
| 25 May | 0% |
| 1 Jun | 0% |
| 8 Jun | 13% |
| 15 Jun | 62% |
| 22 Jun | 73% |
| 29 Jun | 30% |
| 6 Jul | 55% |
| 13 Jul | 48% |
| 20 Jul | 1% |
| 27 Jul | 0% |
| 3 Aug | 0% |
| 10 Aug | 0% |
| 17 Aug | 0% |
| 24 Aug | 0% |
| 31 Aug | 0% |
| 7 Sep | 0% |
| 14 Sep | 0% |
| 21 Sep | 0% |
| 28 Sep | 0% |
What to expect each month
OctoberThis month
Pollen is low. Mould spores outdoors on damp days, and indoor allergens build up as heating comes on and windows stay shut.
November
No pollen to speak of. Winter symptoms usually come from dust mites, mould, pets or a cold.
December
No pollen. Christmas trees can carry mould spores indoors, which is why some people sneeze more over the holidays.
January
Hazel can start in mild spells from late January. Few people notice it. If you have symptoms in January, dust mites, mould or pets indoors are more likely causes.
February
Hazel peaks and alder starts. pollen.ie forecasts start in mid-February.
March
Alder peaks, and ash and willow begin. In 2026, tree pollen first reached Moderate on 2 March and High on 18 March.
April
The worst month for tree pollen, with birch and ash at their peak. Birch is the tree most likely to cause hay fever. On 21 April 2026, 29 of 32 counties were High.
May
Birch tails off and oak takes over. Most years there is a quieter spell before grass arrives. In 2026, May had no High days at all.
June
Grass season, and the worst month for most people with hay fever. Grass first reached High on 6 June 2026, and on 25 June every county was High.
July
Grass carries on, easing from mid-July. Nettle and plantain are in the air, and mould spores rise in warm, humid weather.
August
Grass is mostly over by the first week. Nettle and mugwort continue, and mould spores peak on warm, damp days and around harvest.
September
Weed pollen and mould spores fade. Late-season symptoms are often mould rather than pollen.
High pollen days in 2026, by county
The midlands and east had three to five times as many High days as the west. Pick a county to see its season day by day.
Questions
When is pollen season in Ireland?
From February to September. Tree pollen runs from February to May and peaks in April. Grass pollen runs from late May to early August and peaks from mid-June to mid-July. Weed pollen and mould spores follow from July to September.
When is hay fever worst in Ireland?
Mid-June to mid-July, when grass pollen peaks. On 25 June 2026 every county in Ireland had a High pollen forecast.
Which parts of Ireland get the most pollen?
The midlands and east. In 2026 Carlow and Kildare had 36 High days each, while Galway had 7. Wetter, windier Atlantic weather keeps pollen lower in the west.
Is there pollen in winter?
Very little. Hazel can start in mild spells from late January. Most winter symptoms come from dust mites, mould or pets indoors.
When does birch pollen peak in Ireland?
In April. Birch is the tree pollen most likely to cause hay fever, and its season is usually over by mid-May.