Pollen forecast calculator: see expected tree, grass and weed pollen levels by month for your region and plan allergy meds. Free, runs in your browser.
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General estimate for planning only — not medical advice. Consult a doctor about your specific situation.
Calculation details
Every figure above is calculated locally in your browser from the assumptions shown. No inputs are sent anywhere. See the methodology section below for how this tool works.
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Assumptions to Verify
These tools provide general estimates for planning and education only.
They are not medical advice and not a substitute for a qualified healthcare professional.
Always consult your doctor or another healthcare provider about your specific situation.
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Worked example: reading a grass spike in Austin, TX
Say the feed returns hourly values for two days where grass peaks at 68 grains/m3 and ragweed at 24, while birch reads 1.2, alder 0.4, and olive 0. The calculator scans all 48 hourly points per species and keeps each maximum, so you see 68, 24, 1, 0, 0 after rounding (1.2 rounds to 1, 0.4 rounds to 0).
The bar for each row is the value divided by 3, capped at 100 percent width. Grass draws 68/3 = 23 percent, ragweed 24/3 = 8 percent, birch 1/3 = 0 percent, so two species show no visible bar even though they are not zero. The peak is max(0, 1, 68, 0, 24) = 68, which lands in the 50 to 99 band and prints Moderate (68 peak).
The practical read: grass at 68 grains/m3 is a genuinely high grass day in most published scales, while ragweed at 24 is a warm-up. If your symptoms track grass, this is a day for the antihistamine; if they track ragweed, the worse reading is probably still ahead.
Limits of the free feed: nulls, grid cells, and seasons
The Open-Meteo pollen variables come from the CAMS European and global model ensemble on roughly an 11 km grid, so a reading describes your neighborhood, not your backyard. A street with a single birch row can run several times higher than the grid cell on a spring morning.
Species return null or zero when out of season. In Austin in July, birch and alder will read 0 not because no birch exists but because the model is not emitting for them; olive behaves the same outside the Mediterranean belt. Conversely, in much of the US and Australia the ragweed and olive layers are the least validated, so treat those numbers as directional.
The level bands here (Minimal under 15, Low 15 to 49, Moderate 50 to 99, High 100+) are the calculator's own labels, not a clinical standard. Station-measured counts at the same site can differ 2x from model output on any given day, and no forecast counts the pollen actually inside your house. Use the trend across the two days rather than any single number, and if symptoms are severe, a certified pollen counting station near you is the closer ground truth.
