Understanding Pollen Counts

What Are Pollen Counts?

Pollen counts measure the concentration of pollen grains in the air. These measurements help allergy sufferers anticipate symptom severity and plan their activities accordingly. Understanding what the numbers mean can help you make better decisions about when to go outside and when to take precautions.

How Is Pollen Measured?

Traditional Method: Burkard Traps

Most official pollen monitoring stations use devices called Burkard traps (or Hirst-type samplers):

Air sampling: A pump draws in air at a constant rate (typically 10 liters per minute)
Collection: Pollen grains stick to a greased slide or tape inside the device
Analysis: A trained specialist examines the sample under a microscope
Counting: Each pollen type is identified and counted
Calculation: Results are expressed as grains per cubic meter of air (grains/m³)

This process takes 24-48 hours, which is why pollen reports often reflect yesterday’s conditions rather than today’s.

Modern Approaches

Newer technologies are emerging:

Automatic pollen counters: Use laser technology and AI to identify pollen in real-time
Forecast models: Combine historical data, weather predictions, and phenological information
Satellite data: Help predict regional pollen patterns based on vegetation and weather

The Pollen.city Scale

On Pollen.city, we display pollen levels on a simple 0-5 scale:

Level	Rating	What It Means
0	None	No significant pollen detected
1	Very Low	Minimal impact for most allergy sufferers
2	Low	Some sensitive individuals may notice symptoms
3	Moderate	Many allergy sufferers will experience symptoms
4	High	Most allergy sufferers will experience symptoms
5	Very High	Severe symptoms likely for all allergy sufferers

This scale is normalized across different pollen types, making it easy to compare tree, grass, and weed pollen at a glance.

Why Symptoms Don’t Always Match Counts

You might wonder why you sometimes feel terrible when pollen counts are “low” or feel fine when they’re “high.” Several factors explain this:

Personal Sensitivity

Everyone’s allergy threshold is different
Some people react to very small amounts of pollen
Cross-reactive allergies can amplify symptoms

Measurement Limitations

Counts are taken at specific locations and may not reflect your exact area
There’s usually a delay between sampling and reporting
Different species within a category affect people differently

Environmental Factors

Humidity: High humidity can cause pollen to rupture, releasing smaller allergenic particles
Pollution: Air pollution can make pollen more allergenic
Thunderstorms: Can break pollen into smaller, more penetrating particles

Priming Effect

Repeated exposure during the season makes your immune system more reactive
Early-season pollen “primes” your body to react more strongly later
This explains why symptoms often worsen as the season progresses

Weather and Pollen

Weather significantly affects pollen levels:

Wind

Calm days: Pollen stays closer to its source
Breezy days: Pollen spreads over larger areas
Strong winds: Can carry pollen hundreds of kilometers

Rain

During rain: Pollen is washed from the air (temporary relief)
After rain: Counts stay low briefly before rising again
Thunderstorms: Can actually worsen allergies by rupturing pollen grains

Temperature

Warm, sunny days: Promote plant growth and pollen release
Cool days: Slower pollen production
Early spring warmth: Can trigger earlier, more intense pollen seasons

Time of Day

Morning (6-10 AM): Many trees and grasses release pollen as temperatures rise
Midday-Afternoon: Pollen is carried higher and spreads further
Evening: Pollen settles as air cools
Night: Generally lower pollen levels

Pollen Types Explained

Tree Pollen

Season: Late winter to late spring (varies by species)
Notable species: Birch, oak, maple, alder, hazel, pine
Characteristics: Light, wind-dispersed, can travel long distances

Grass Pollen

Season: Late spring to early fall
Characteristics: Most common cause of hay fever, affects up to 95% of pollen allergy sufferers
Peak: Usually June-July in Northern Hemisphere

Weed Pollen

Season: Late summer to fall
Notable species: Ragweed, mugwort, plantain
Characteristics: Ragweed is particularly potent; one plant can produce billions of pollen grains

Making the Most of Pollen Forecasts

Check Daily

Pollen levels can change significantly day to day. Make checking the forecast part of your morning routine, especially during peak season.

Plan Ahead

If high pollen days are forecasted:

Take medications preventatively
Schedule outdoor activities for lower-pollen times
Have backup indoor plans

Know Your Triggers

Track which pollen types affect you most and pay special attention to their forecasts. Not all types affect all people equally.

Consider Multiple Days

A few consecutive high-pollen days can have a cumulative effect on symptoms. Factor in recent exposure when planning activities.