Tree pollen

Google pollen · 0–5 · the day

Oak catkins shedding pollen — White oak catkins shedding pollen in April. Photo: Famartin, CC BY-SA 4.0.

What it is

Tree pollen on a 0–5 scale, by kind of tree.

How it affects breathing

Evidence. Mostly a hay-fever story; the asthma evidence is thin, so these warn later than grass does.
How likely. Spring, and which trees depends on the region; oak and birch are the big ones in the eastern US. For people sensitized to tree pollen, which most people with allergic asthma are, nose and eye symptoms are near-certain in season; asthma symptoms follow in a smaller share, mostly with a cold on top.
What helps. A daily antihistamine or steroid nose spray started before the season, a daily controller inhaler kept up through it, windows shut and a shower after time outdoors on high days. Allergy shots are the one treatment that changes the allergy itself rather than the symptoms.

How Breathing Index measures it

Your Breathing Index takes the day’s value, since Google’s model resolves pollen by the day and the tree-pollen evidence does not support a longer window.

Where the number comes from

Estimated by Google’s pollen model from land cover and weather, not counted with an instrument. A season calendar fills in where the model is silent, and says so.

Breathing Index is a breathing lens on public air data — not medical advice. Trust your symptoms and your asthma action plan over anything on this screen.