If hay fever shapes part of your year, it helps to know roughly when the harder weeks tend to arrive. That is exactly what a pollen calendar UK sufferers can lean on gives you: a gentle map of when tree, grass and weed pollen are usually about, so the season feels a little less like a surprise and a little more like something you can plan around.
This guide keeps things calm and clear. It walks through the year month by month, explains why grass pollen matters most for so many people, and offers small, practical steps for the higher days. There is nothing to sign up for and no rush. The aim is simply to help you feel prepared, not worried.
Key facts at a glance
- Tree pollen comes first, typically from late March to mid-May, and affects around 25% of people with hay fever (Met Office).
- Grass pollen runs from mid-May until July, with two peaks — and most people who have hay fever react to it, making it the UK's biggest trigger (Met Office).
- Weed pollen covers roughly the end of June to September (Met Office).
- The exact timing shifts each year with the weather, and starts earlier in the milder south than the cooler north (Met Office).
- There is no permanent solution for hay fever, but a pharmacist can suggest ways to ease symptoms (NHS).
What a pollen calendar is, and how the UK one works
A pollen calendar is a simple year-long guide showing when different pollens are usually in the air. In the UK, the three that matter for hay fever are tree, grass and weed pollen, and each has its own season. Read together, they explain why some months feel far harder than others.
The UK's pollen information comes from the National Pollen and Aerobiology Research Unit at the University of Worcester, which produces the pollen forecast the Met Office publishes. Pollen is collected from monitoring sites, counted, and combined with the weather to forecast the days ahead. That is the science quietly sitting behind the calendar.
A calendar is a guide to the *typical* pattern, not a promise about any single day. Your own street, garden or local park may feel a little different, depending on the plants nearby and which way the wind is blowing. So think of it as the shape of the season, with the daily forecast filling in the detail.
Pollen calendar UK: month by month
Here is the UK pollen year at a glance. Tree pollen leads in spring, grass takes over from mid-May and is the dominant summer trigger, and weeds carry the season into early autumn. The table below shows when each type is usually building, at its peak, or fading — a quick way to read the pollen calendar UK households plan around.
| Month | Tree pollen | Grass pollen | Weed pollen |
|---|---|---|---|
| January–February | Low (early hazel/alder possible) | — | — |
| Late March | Rising | — | — |
| April | High / peak (incl. birch) | — | — |
| Early–mid May | Fading | Rising | — |
| Late May | — | Rising to high | — |
| June | Low | Peak (first peak) | Building |
| July | — | High (second peak) | High |
| August | — | Fading | High |
| September | — | — | Fading |
| October–December | Low | Low | Low |
Windows are typical UK averages from the Met Office; birch is included as a notably allergenic spring tree. Timings run a little earlier in southern England and a little later in northern Britain and at altitude.
When does tree pollen peak in the UK?
Tree pollen is the first of the season, typically appearing from late March to mid-May, and it affects around 25% of people with hay fever, according to the Met Office. So if your symptoms reliably start in early spring, well before the summer, trees are the most likely reason.
A handful of trees produce most of the trouble. Birch is among the most allergenic in the UK and tends to be at its strongest through April and into early May, which is often when tree-sensitive people notice the sharpest few weeks. Hazel and alder can release small amounts even earlier, sometimes in late winter.
If spring is consistently your hardest stretch, the tree window is worth marking on your own calendar. Knowing it is coming means you can start your usual gentle routines a little sooner, rather than being caught out by the first warm, breezy days of the year.
When does grass pollen peak — and why it matters most
Grass pollen is the UK's biggest hay fever trigger: the Met Office notes that most people with hay fever react to it. Its season runs from mid-May until July, and unusually it has two peaks — a larger one in early summer and a smaller second one a few weeks later — which is why symptoms can dip and then return.
This is the stretch most people mean when they talk about "hay fever season". Because grass is so widespread — verges, parks, playing fields, gardens — it is hard to avoid entirely, and warm early-summer weather can push counts up quickly. If June and July are your worst weeks, grass is almost certainly the cause.
The two-peak pattern is genuinely useful to know. A quieter spell in the middle of the season does not mean it is over; a second rise often follows. Watching the daily forecast across these weeks, rather than judging by one good day, gives you a truer picture of what your summer is doing.
When does weed pollen peak in the UK?
Weed pollen is the last main season, covering roughly the end of June to September, so it overlaps with late grass and then carries hay fever into early autumn. Nettles, docks, plantain and mugwort are common UK culprits. If your symptoms linger into September, weeds are a likely reason.
Weed pollen can be released across a long window, which is part of why some people feel they never quite get a clear run. It tends to be less intense than the peak of grass season for most sufferers, but for those who react to it, late summer and early autumn can be their most noticeable time of year.
Because weeds thrive on waste ground, roadsides and untended corners, local surroundings matter here more than most. A patch of nettles near your usual walk or a neglected verge by the office can make your own experience differ from the wider forecast — another reason your personal pattern is worth watching.
Why the pollen calendar shifts from year to year
A pollen calendar shows the typical pattern, but the exact dates move each year because the weather sets the pace. Warm, humid and windy days tend to lift counts, while a good spell of rain can wash pollen out of the air. Where you live in the UK matters too, so no two seasons line up perfectly.
The Met Office points out that the season starts at different times depending on where you are, generally earlier in the milder south and later further north and at altitude. A mild spring can bring the tree season forward; a cool, wet one can hold it back. This is why the calendar is a reliable *shape* rather than a fixed set of dates.
Weather also explains why two days in the same week can feel so different. A warm, still afternoon may leave you streaming, while the morning after heavy rain often feels easier. Pairing the calendar's big picture with the daily forecast is the most realistic way to read your own year.
What you can do with the pollen calendar
Use the calendar to get ahead of your own difficult weeks, then let the daily forecast handle the detail. If you know grass is your trigger, for example, you can plan gently around June and July — starting simple habits a little earlier rather than reacting once symptoms have already built up.
A few small routines help on higher days. You might keep windows closed at the busiest times, dry washing indoors, wear wraparound sunglasses outside, and rinse your face or change your top after being out, so you carry less pollen home. Leaving shoes and outer layers by the door, and wiping pets after a walk, keeps a little more of it outdoors.
It also helps to keep a simple note of how you feel alongside what the pollen was like. Over a season a gentle pattern usually appears, and that pattern is genuinely useful — it tells *you* which pollens affect you and when, which is far more personal than any national calendar can be.
If your symptoms are persistent, uncomfortable, or getting in the way of daily life, please speak to a pharmacist or GP. As the NHS notes, there is no permanent solution for hay fever, but a pharmacist can suggest treatments to ease it. PEPA is here for the everyday picture, not to replace that conversation.
In short
The UK pollen calendar has a clear shape: trees in spring from late March to mid-May, grass — the biggest trigger — from mid-May to July, and weeds from the end of June into September. The exact dates shift each year with the weather and where you live. Knowing your own trigger and its window helps you feel prepared rather than caught out, and small, calm habits often make the biggest difference on the higher days.
See your personal allergy picture today
See how the pollen calendar looks where you actually are. PEPA gives you a calm, local view of the day ahead and lets you note how you feel over time, with nothing to share and no account to set up. Many people find it a gentle way to learn their own pattern across the season.
Frequently asked questions
What is a pollen calendar for the UK?
It is a simple year-long guide showing when tree, grass and weed pollen are usually in the air across the UK. Trees come first in spring, grass dominates early summer, and weeds run into early autumn. It shows the typical pattern rather than any single day's count.
When is the worst month for hay fever in the UK?
For most people it is June or July, when grass pollen — the UK's most common trigger — is at its peak. If trees affect you instead, April and early May can be harder; if weeds do, late summer into September may be your worst stretch.
When does grass pollen season start and end in the UK?
Grass pollen season typically runs from mid-May until July, according to the Met Office, and it has two peaks — a larger one in early summer and a smaller one a few weeks later. Because grass is so widespread, it is the UK's most common hay fever trigger.
Does the pollen calendar change each year?
Yes. The calendar shows the typical pattern, but the exact timing shifts each year with the weather. Warm, humid, windy spells push counts up, while rain brings them down, and the season starts earlier in the milder south than the cooler north.
How do I know which pollen affects me?
The most reliable guide is your own pattern watched over a season. If spring is hardest, trees are likely; early summer points to grass; late summer suggests weeds. A simple diary alongside the daily forecast helps reveal what a higher day feels like for you.
Can PEPA help me follow the pollen calendar?
Yes. PEPA shows your local pollen picture day by day and lets you log how you feel alongside it, so the national calendar becomes something personal — a picture of which pollens affect you, and when, that builds up over time.
Read next
References
- Tree pollen season in the UK typically runs from late March to mid-May and affects around 25% of people with hay fever. — Met Office, When is hay fever season. Source (checked 2026-07-16).
- Grass pollen season runs from mid-May until July, has two peaks, and most people who have hay fever react to it, making it the UK's most common trigger. — Met Office, When is hay fever season. Source (checked 2026-07-16).
- Weed pollen season typically covers the end of June to September, and hay fever season starts at different times depending on where you live in the UK. — Met Office, When is hay fever season. Source (checked 2026-07-16).
- There is currently no cure for hay fever, but a pharmacist can give advice and suggest treatments to ease symptoms. — NHS, Hay fever. Source (checked 2026-07-16).
- The UK pollen forecast is produced by the National Pollen and Aerobiology Research Unit at the University of Worcester. — University of Worcester, National Pollen and Aerobiology Research Unit. Source (checked 2026-07-16).
- General information on hay fever and seasonal pollen allergy in the UK. — Allergy UK, Hay Fever. Source (checked 2026-07-16).
Image credits
- Photo by neslihan ୨ৎ on Pexels.
- Photo by Julia Volk on Pexels.
- Photo by Lif 4Gd on Pexels.
PEPA shares general lifestyle information only. It is not medical advice, and it does not replace guidance from a pharmacist or GP. Please speak to them about your symptoms or any health concerns.