Understanding Pollen Counts
What Are Pollen Counts?
Pollen counts measure how much pollen is in the air. These measurements help allergy sufferers anticipate how bad their symptoms might be and plan their activities accordingly. Understanding what the numbers mean can help you make better decisions about when to go outside.
How Is Pollen Measured?
Traditional Method: Burkard Traps
Most official pollen monitoring stations use devices called Burkard traps (or Hirst-type samplers):
- A pump draws in air at a constant rate (typically 10 liters per minute)
- Pollen grains stick to a greased slide or tape inside the device
- A trained specialist examines the sample under a microscope
- Each pollen type is identified and counted
- 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 feel terrible when 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 tiny amounts of pollen. Cross-reactive allergies can also 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, and 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 is why symptoms often worsen as the season goes on.
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: The most common cause of hay fever, affecting up to 95% of pollen allergy sufferers
- Peak: Usually June-July in the Northern Hemisphere
Weed Pollen
- Season: Late summer to fall
- Notable species: Ragweed, mugwort, plantain
- Characteristics: Ragweed is particularly potent — a single 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 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 everyone reacts to everything.
Consider Multiple Days
A few consecutive high-pollen days can have a cumulative effect on symptoms. Factor in recent exposure when planning activities.