Start with the date
Start with the dates shown on your city page. Each forecast covers four days.
A forecast predicts a concentration. A measurement comes from sampling the air. City pages show model estimates, not readings from a sensor in that city. The methodology page explains the source and its limitations.
Read the unit before the number
Grains/m³ means pollen grains per cubic metre of air. PollenCount displays the highest available hourly value for each type and date. When every expected hour is present, that is the daily maximum. It is not the daily average or the concentration throughout the entire day.
For example, imagine a complete day whose hourly values are mostly 10, with a peak of 35. Its daily maximum is 35. The maximum alone does not tell you how long the peak lasted. This is an illustrative example, not a forecast.
Distinguish zero, partial and missing
- 0: the available model values are zero. This is a numeric result, not proof that every airborne allergen is absent.
- Partial · 20/24 hours: four expected hourly values are unavailable. The displayed maximum describes only the 20 available hours.
- — No forecast: there is no usable value for that type and day. It must not be read as zero.
Days are grouped using Europe/London time. Clock changes mean a complete day can contain 23 or 25 hours rather than 24.
Compare the same thing
Compare one pollen type across dates using the numbers in its row. Each small trend chart has its own vertical scale, so equally tall lines do not necessarily represent equal concentrations.
The overview highlights the highest pollen level among the selected types. Choose a known trigger to follow its forecast on its own; types reaching the same moderate or high band are shown together.
Understanding pollen levels
City pages show descriptive pollen levels alongside the concentrations. Choose a pollen type to follow and a sensitivity option for relevant general guidance. The level describes the highest hourly concentration in a complete day; it is not a symptom probability. Partial dates have no full-day level and are excluded from comparisons.