Pollen season

Birch trees stretching up to the sun as if seen by someone lying on their back in a forest – birch is on our pollen calendar

Pollen season is that frantic time of year when plants rush to reproduce. They do this by releasing the tiny grains to be fertilized by other plants, possibly many miles away.

Plants have evolved different ways to spread their pollen. Some rely on insects or animals (pollinators) to carry it from flower to flower. Others use water. And about 12% of plants send out their pollen to travel on the wind.

If you have hay fever, you’ll want to know about the windborne pollen season. Plants tend to release billions of the tiny grains to make sure some hit the spot. Pollen can end up in your nose and eyes, cause allergic reactions and trigger allergic rhinitis. Our pollen calendars below and in the klarify app tell you when some of the sneeziest types of pollen tend to be filling the air.

As to your personal pollen season, that will depend on your allergy trigger, the weather and where you live. Read on to find out how all that works and how to control seasonal allergies with the help of pollen data.

So when is pollen season?

Some plants may produce pollen all year round in warmer parts of the world. And mild winters in temperate climates can trigger plants to release pollen early. Generally, though, pollen season spans spring, summer and fall. It starts with tree pollen, when the conditions are right.

Plants have all evolved their own best way to keep their species going. Flowering in the spring before the leaves are properly out means they won’t get in the way of the cloud of pollen. Trees usually release their pollen when temperatures rise to 55F.

Day length is important for some plants at the other end of pollen season. For instance, ragweed and mugwort like it when the days are shorter than the nights so they flower from late summer into the fall.

Pollen season usually ends with the first big frost. It kills off much of the plant life that contributes to hay fever problems. So winter tends to be the easiest time for people with pollen allergies because they will have fewer symptoms.

Allergies are an overreaction of your immune system

Tree pollen season
  • Tree pollen is finer than many other types. The wind can carry it for hundreds of miles from its origin.
  • Spring can get very sneezy in cities because tidiness obsessed town planners prefer male trees.
  • Why? It’s the males that release tree pollen. Females make the seeds and the fruit that can clog up sidewalks.
Grass pollen season
  • Sensitization is the first step in developing an allergy. Among plant allergens, grass pollen is perhaps the most potent sensitizer.
  • In 2015 lawn covered up to 75% of green open spaces in cities.
  • Keeping your lawn mown to 2 inches high can stop it from flowering and releasing grass pollen.
Weed pollen season
  • Two of the biggest weedy troublemakers, mugwort and invasive ragweed, are cousins. They’re both members of the daisy family.
  • It can take as few as 10 ragweed pollen grains to trigger hay fever and peak levels can be 250 grains per cubic meter (35ft3) of air.
  • Ragweed and mugwort pollen can give you an allergic rash too if it lands on your skin.

Which season is worse for pollen?

It depends which pollen you're allergic to. We've talked a bit about that already. Trees tend to pollinate in the spring, grass in the summer and weeds in the fall. But you'll see from the pollen calendar that pollen season for one type of plant can overlap with another.

Weather plays a big part too. Sun, wind, rain and humidity can impact on pollen allergy symptoms. Trees usually release more pollen during a period of low rainfall. And pollen can travel further in the air when it’s dry. It’s not just changing conditions day to day that can impact allergy symptoms. Rising temperatures from climate change are doing it too. Pollen season for trees, grass and weeds has lengthened by 20 days in three decades. And pollen concentrations have increased by 21%.

How will pollen season affect me?

Mild hay fever or allergic rhinitis can be annoying and mean you have to carry tissues with you until pollen season ends. But the symptoms could also have a far greater impact on your life. You might have watery eyes, a stuffy or runny nose, post-nasal drip or a cough. This can make it harder to sleep at night so that you feel tired all day. And it can have quite an impact on your life. You might have to take time off work or stop outdoor activities you enjoy. Hay fever can also worsen lower respiratory symptoms and make you prone to getting sinusitis. And it's often a factor in ear infections in children.

Children with allergic rhinitis may miss school days too. Symptoms can affect their exam results during peak pollen seasons and they may do less well at sport. A diagnosis of attention deficit hyperactivity disorder (ADHD) is not uncommon. Understandably all this can affect children's self-esteem and be stressful for parents.

Want to know about
hay fever in kids?

Boy reading a book on his mother’s knee – they’re under a tree which could be challenging if he had pollen allergies

Why is my pollen season so long?

Sometimes it's obvious what's causing your symptoms. For example, if you start sneezing when you're near birch trees, certain grasses, mugwort, ragweed or tumbleweed (Russian thistle) when they're flowering. At other times it may be difficult to pinpoint, especially if it lasts more than one allergy season. Track your symptoms on our app to help you to identify what's causing them.

If your pollen allergies last more than one calendar season it could be due to a cross-reaction. Different pollens contain very similar proteins. And your immune system may react to these proteins too. For instance, people who are allergic to birch may also react to other tree pollens like alder, hazel, hornbeam and oak, all of which flower at slightly different times. Grass (summer flowering) and mugwort (fall) have similar proteins too. This could extend your allergy season from weeks to months.

Cross-reactions can also happen when you eat fresh fruit and vegetables that have proteins similar to your problem pollen. It's known as oral allergy syndrome(OAS) or pollen food syndrome (PFS). Symptoms are usually mild and local and you may notice it more when your seasonal allergies are playing up.

Finding out your pollen season trigger(s)

A look at the pollen calendar can give you a clue as to what you might be allergic to. It’s local to you.

A few studies have looked at the pollen season across North America as a whole. These have often focused on changes over time rather than comparing regions. But different plants may be common causes of hay fever depending on where you live. For instance, you’ll see alder on four out of five of our US pollen calendars but not the Northeast. And the same plant may come into flower at a slightly different time. Grass in South Central US can start as early as February.

1 Pollen calendar for Southeast US
Pollen calendar for the Southeast US showing when trees, grass and weeds release their pollen and may cause hay fever
2 Pollen calendar for South Central US
Pollen calendar for the South Central US showing when trees, grass and weeds release their pollen and may cause hay fever
3 Pollen calendar for Northeast US
Pollen calendar for the Northeast US showing when trees, grass and weeds release their pollen and may cause hay fever
4 Pollen calendar for Midwest US
Pollen calendar for the Midwest US showing when trees, grass and weeds release their pollen and may cause hay fever
5 Pollen calendar for Western US
Pollen calendar for the Western US showing when trees, grass and weeds release their pollen and may cause hay fever

Note down your symptoms and tell your healthcare provider about your detective work with the pollen calendar. They'll want to know your medical history and if allergies run in your family. To help make a diagnosis they may suggest allergy testing too. That's likely to be a skin prick test or a blood test. Or both if the skin prick test was inconclusive. Your healthcare provider will tell you about the treatment options for your allergy and offer advice on how to avoid your triggers during pollen season.

Why data is your pollen season friend

Data sounds very...post-millennial. But pollen counts actually started in the 1960s. William Frankland, a British allergist, wanted to find a way to help his patients control their hay fever symptoms (he got them too). Using a pollen trap on the roof of the London hospital where he worked, he was able to report the daily pollen count to the national press. Now it's much easier to get pollen updates wherever you are. They're here on our website and in our allergy app, provided by our partner BreezoMeter.

BreezoMeter uses technology and advanced analytics to provide location-based air quality and pollen data in more than 65 countries worldwide. Type where you are or where you want to know about into the search box at the top of this page to check today’s pollen levels. In our app, you can also get a 3-day pollen forecast for specific tree, grasses and weed pollen. There’s information about air quality and the weather too. Both can affect pollen levels and aggravate respiratory allergy symptoms.

Before pollen season

  • Look at our pollen calendar to find out when your pollen season is due to start. And set yourself a reminder on your phone.
  • Leftover medicines from the previous year could have expired. If so, they may not work and could even be unsafe. Time to stock-up. And check if the same symptom-relieving medications are still right for you. Many antihistamines and corticosteroids are available as over-the-counter or with a prescription. Decongestants can also help with a blocked nose.
  • Speak to your pharmacist or healthcare provider about using an antihistamine or corticosteroid from two weeks before your pollen season starts. This might help reduce allergy symptoms when the pollen starts flying
Our allergy app

Put our smiley icon on your homescreen. It’s a smart way to manage hay fever, with up-to-date pollen info for where you are and tips tailored to you.

 If you’re affected by weed pollen allergy the klarify app can help you track your symptoms so you can manage your day

During pollen season

  • Use the daily pollen report, weather and air quality for your area to plan your day – and the 3-day pollen forecast on our app to plan further ahead.
  • Keep doors and windows closed if the day is looking particularly sneezy.
  • Set your car’s air-conditioning to recirculate to keep pollen out. Just remember to change the filter regularly.
  • Take symptom-relief medication before going out. Antihistamines usually need one to two hours to become effective.
  • Rinse your nasal passages with saline several times a day to keep them clear of irritants. This may reduce allergy symptoms.
  • Wear a sun-hat, wrap-around sunglasses and a face mask when outside.
  • Change your clothes when you get back, dry them inside and wash your hair before you go to bed.

After pollen season

Now you’ve remembered what pollen season is like, maybe it’s time to think about long-term treatment and whether it might be suitable for you.  

Long-term treatment for pollen season symptoms?

Antihistamines, corticosteroids and decongestants can only provide short-term relief. You’ll probably need to take them again when you breathe in pollen next time. But there is a treatment that could reduce your need for these allergy medicines.

Allergy immunotherapy tackles the underlying cause of your symptoms. It gradually trains your immune system to react less strongly to pollen. It's a form of desensitization and involves taking repeated tiny doses of your trigger, either as injections (allergy shots) or tablets. A full course of treatment takes three to five years. The lasting effects vary from person to person. But the goal is to lessen your hay fever during pollen season and the need for symptom-relieving medication.

Maybe it's time to talk to an allergy specialist? Our Find a doctor tool can help you search for one nearby.

Share your story

If you've read all the way to the end of this article about your pollen season, thank you. We'd love to know what you think. Have you tried our app or any of the tips we've suggested? Or do you have any of your own that you'd like to share with others? Head over to klarify on Facebook or Instagram, or email us and share your story.

klarify takes allergy science and makes it simple, and we have rigorous process for doing this. We use up-to-date and authoritative sources of information. Medical experts review our content before we share it with you. They and the klarify editorial team strive to be accurate, thorough, clear and objective at all times. Our editorial policy explains exactly how we do this.