Questions about this forecast

The Copernicus Atmosphere Monitoring Service, which runs an ensemble of European air-quality models and publishes a four-day pollen forecast on a roughly ten-kilometre grid. We download one forecast per day and average the grid cells inside each region. Nothing here is a measurement — it is a model.

No. A count is what a Hirst trap physically catches at one address over 24 hours. This is a model's estimate averaged across a whole region. The two agree on timing far better than on magnitude, and where we can compare them we say so.

Grains per cubic metre of air, the same unit counting stations report, so you can compare them with a national network directly.

Against a Dutch counting station over 113 paired days, our grass levels matched the station's own level on about half of them and were within one level step on nearly all. The model tracks the shape of a season well and its absolute magnitude less well — it reads roughly one and a half times below a point trap.

Either the forecast has not been published yet today, or the region has no grid cells over land in the model domain. Very small regions and some islands fall into the second case.

Because there is almost no pollen in the air. Alder starts in January and everything else is later. Grey means no data; the palest green means measured but negligible.

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