When is pollen worst in Castro Valley?

Tree pollen jumps the gun in Castro Valley, opening as early as Jan–Apr while colder regions are still dormant. Grass follows Mar–Jun and ragweed closes the year Aug–Oct. The early tree start is the trap — symptoms can begin before you expect them. Currently, grass pollen is what's driving counts this month.

What's in the air in Castro Valley right now?

Right now grass pollen leads in Castro Valley at a Moderate (3/5) level. The species actually in the air today: Pine, Oak, and Grasses. On a quiet live day, Castro Valley's seasonal calendar fills in what's typically airborne this time of year.

Is tree or grass pollen higher in Castro Valley in spring?

In spring, tree pollen leads in Castro Valley — trees pollinate Jan–Apr, ahead of grass (Mar–Jun). The handoff is the tail of the tree window: tree counts taper as grass climbs, so an early-spring flare is more likely tree pollen and a late-spring one more likely grass.

What makes Castro Valley's pollen season distinctive?

Castro Valley sits in the mild Mediterranean California zone, which means an early start — mild winters pull tree pollen forward into late winter, ahead of a spring grass peak and a relatively contained ragweed fall. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in Castro Valley?

Through Castro Valley's peak windows (tree Jan–Apr, grass Mar–Jun, ragweed Aug–Oct), keep windows shut and run AC on recirculate; counts run highest on dry, warm, windy mornings, so push outdoor activity to late afternoon or just after rain, which clears pollen from the air. A HEPA purifier indoors, a saline rinse after being outside, showering before bed, and starting antihistamines a week or two before your worst local window all measurably cut symptoms.

What pollen index counts as high?

Pollen is reported on a categorical scale — None, Low, Moderate, High, and Very High. "High" and above means most allergy sufferers notice symptoms even with brief outdoor exposure, and sensitized people should limit time outside and pre-medicate. "Low" to "Moderate" usually only affects highly sensitive individuals.

Castro Valley, California Pollen Count

Castro Valley pollen count and allergy forecast — tree, grass, and ragweed seasons and what’s pollinating now

Castro Valley, CA · Pollen count right now

Grass pollen is Moderate in Castro Valley today

Grass: Moderate 3/5Tomorrow: Moderate

Today’s pollen by type

TreeVery Low1/5
GrassModerate3/5
Weed / RagweedOut of season

Active now: Pine, Oak, Grasses.

Castro Valley pollen calendar

Typical peak months for each pollen type in this climate region. The highlighted column is the current month.

JFMAMJJASOND

TreeJan–Apr

GrassMar–Jun

WeedAug–Oct

Allergy relief

Zyrtec 24-Hour Allergy Relief (Cetirizine 10 mg)
A once-daily, non-drowsy oral antihistamine. Start it a couple of weeks before your worst pollen season for the best symptom control.
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NeilMed Sinus Rinse Kit (Saline Nasal Irrigation)
A saline rinse physically flushes pollen out of the nasal passages. Use it after time outdoors during peak season to cut the allergen load before symptoms build.
View on Amazon →

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How Castro Valley’s pollen count works

The calendar above is tuned to Castro Valley’s mild Mediterranean California climate, not a national average: tree pollen peaks Jan–Apr, grass Mar–Jun, and ragweed Aug–Oct here. Those windows are why grass pollen is the one in season in Castro Valley right now.

Right now grass pollen leads in Castro Valley at a Moderate (3/5) level. The species actually in the air today: Pine, Oak, and Grasses. Counts run highest on warm, dry, windy mornings and drop after rain, which washes pollen out of the air — reported on the None / Low / Moderate / High / Very High scale.

Frequently asked

When is pollen worst in Castro Valley?: Tree pollen jumps the gun in Castro Valley, opening as early as Jan–Apr while colder regions are still dormant. Grass follows Mar–Jun and ragweed closes the year Aug–Oct. The early tree start is the trap — symptoms can begin before you expect them. Currently, grass pollen is what's driving counts this month.
What's in the air in Castro Valley right now?: Right now grass pollen leads in Castro Valley at a Moderate (3/5) level. The species actually in the air today: Pine, Oak, and Grasses. On a quiet live day, Castro Valley's seasonal calendar fills in what's typically airborne this time of year.
Is tree or grass pollen higher in Castro Valley in spring?: In spring, tree pollen leads in Castro Valley — trees pollinate Jan–Apr, ahead of grass (Mar–Jun). The handoff is the tail of the tree window: tree counts taper as grass climbs, so an early-spring flare is more likely tree pollen and a late-spring one more likely grass.
What makes Castro Valley's pollen season distinctive?: Castro Valley sits in the mild Mediterranean California zone, which means an early start — mild winters pull tree pollen forward into late winter, ahead of a spring grass peak and a relatively contained ragweed fall. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in Castro Valley?: Through Castro Valley's peak windows (tree Jan–Apr, grass Mar–Jun, ragweed Aug–Oct), keep windows shut and run AC on recirculate; counts run highest on dry, warm, windy mornings, so push outdoor activity to late afternoon or just after rain, which clears pollen from the air. A HEPA purifier indoors, a saline rinse after being outside, showering before bed, and starting antihistamines a week or two before your worst local window all measurably cut symptoms.
What pollen index counts as high?: Pollen is reported on a categorical scale — None, Low, Moderate, High, and Very High. "High" and above means most allergy sufferers notice symptoms even with brief outdoor exposure, and sensitized people should limit time outside and pre-medicate. "Low" to "Moderate" usually only affects highly sensitive individuals.

More for Castro Valley

See the full Castro Valley, CA weather forecast — hour-by-hour outlook, NOAA radar, satellite, and air quality.