How Pollen Forecasts Work
Pollen forecasts predict airborne pollen levels based on plant phenology (growth cycles), weather conditions, and historical data. Counts are measured in grains per cubic metre of air.
Pollen Season Calendar
| Season | Primary Pollen | Months |
|---|---|---|
| Early Spring | Tree pollen (birch, oak, cedar) | February-April |
| Late Spring | Grass pollen | May-July |
| Summer-Fall | Weed pollen (ragweed) | July-October |
| Variable | Mould spores | Year-round, peak in damp periods |
Weather and Pollen
| Weather Condition | Effect on Pollen |
|---|---|
| Warm, dry, windy | Highest pollen — wind carries it far |
| After rain | Pollen drops temporarily (washed out) |
| During rain | Thunderstorm asthma risk — rain breaks pollen into finer particles |
| Cool, damp | Lower pollen levels |
| High humidity | Moulds increase, tree/grass pollen decreases |
Pollen Count Levels
| Level | Grains/m³ (grass) | Symptoms |
|---|---|---|
| Low | 0-29 | Minimal for most people |
| Moderate | 30-59 | Sensitive individuals affected |
| High | 60-149 | Most allergy sufferers symptomatic |
| Very High | 150+ | Severe symptoms likely |
Practical Tips
- Check pollen counts in the morning before opening windows
- Pollen is highest in the early morning (5-10 am) — exercise later
- Shower and change clothes after outdoor activity
- Keep car and home windows closed on high-count days
- Dry laundry indoors during peak season
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