Marathon Eryri - Pollen and Air Quality Forecast for Today
Pollen levels are low today, with mugwort as the main active species. Air quality along the route is good, with all pollutants at low levels. Based on Airmine's forecast, which uses satellite data to calculate exposure every 200 metres along the route, air quality is at its worst 0.0 km after start. Pollen exposure peaks at 32.8 km after start.
To prepare for your activity, use the Airmine app to check the Marathon Eryri forecast before heading out.
Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team
Follow your pollen exposure and performance with the free Airmine–Strava integration. See your pollen and air quality exposure for every Strava activity.
Marathon Eryri runs through the Snowdonia National Park mountain landscape in Wales, with heather, sessile oak, and mountain grassland as the main pollen sources along this demanding Welsh mountain marathon route. The very wet Welsh Atlantic climate provides very frequent rainfall interruptions, while birch peaks through April and May in the lower valleys, grass through June and July on the upland sections, and the October race date falls after the main season throughout this spectacular Welsh mountain marathon.
Today - 10 August
Pollen
Alder (Alnus):
None
0/100
Birch (Betula):
None
0/100
Hazel (Corylus):
None
0/100
Cypress (Cupressaceae):
None
0/100
Grass (Poaceae):
None
0/100
Willow (Salicaceae):
None
0/100
Oak (Quercus):
None
0/100
Mugwort (Artemisia):
Low
9/100
Mulberry (Morus):
None
0/100
Eucalyptus (Myrtaceae):
None
0/100
Plane (Platanus):
None
0/100
Nettle (Urtica):
None
0/100
Acacia (Acacia):
None
0/100
Ragweed (Ambrosia):
None
0/100
Air Quality
PM2.5 (fine particles):
Good
3.8/100
PM10 (coarse particles):
Good
1.4/100
NO2 (nitrogen dioxide):
Good
3.6/100
O3 (ozone):
Good
16.7/100
SO2 (sulfur dioxide):
Good
2.1/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
2.8/100
PM1 (ultrafine particles):
Good
2.6/100
Levels show the highest exposure along the full route
Other routes:
Frequently Asked Questions
Where is air quality worst on the Marathon Eryri route?
Based on today's forecast, O3 is forecast at good levels along the route today (16.7/100). Air quality is at its worst after 0.0 km into the route. Airmine calculates exposure at 200m intervals along the course using satellite-derived atmospheric data.
Where is pollen highest on the Marathon Eryri course?
Pollen exposure peaks at km 32.8 today. This changes through the season as different pollen species become active.
When is pollen worst during the Marathon Eryri season?
October coincides with peak mugwort season. Grass pollen typically rises in May-June.
How often is this forecast updated?
Updated four times daily. See the timestamp below for the most recent update.
Are pollen levels in Marathon Eryri based on measurements or forecasts?
Pollen data is often misunderstood. Most "pollen levels" are not real-time measurements, but forecasts.
Direct pollen measurements are typically delayed by 1-2 days because they require manual analysis. To show current conditions in Marathon Eryri, modern forecasts combine recent measurements, weather data, and information about local vegetation.
This allows us to estimate pollen levels for today and the coming days, not just report the past.
Airmine’s atmospheric monitoring platform was developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team, using satellite and Earth observation technologies to improve emissions monitoring.
Levels show the highest exposure along the full route. Airmine uses satellite data to calculate pollen and air quality every 200 metres along each race route, updated four times daily.
Data provided by Airmine — Last update: 10 August 2026 at 02:34 CEST (Data is updated four times daily.)
This forecast is produced independently using Airmine's own atmospheric data and models.
Unless explicitly made clear, the content on this site has not been paid for by external organisations and is Airmine's sole responsibiity.
Disclaimer: Forecasts are provided for informational purposes only and should not be relied upon as medical advice. Actual pollen and air quality conditions may vary from the forecast. If you have allergies, asthma, or another medical condition, consult a healthcare professional. Please see our Terms of Service for important information about limitations of liability.