When is pollen worst in San Juan?

There's barely an off-switch for grass in San Juan — it pollinates year-round, so the usual "three waves" calendar flattens into a near-constant grass baseline. Tree pollen still spikes Jan–Apr and ragweed adds a Sep–Nov layer on top. Currently, grass pollen is what's driving counts this month.

What's in the air in San Juan right now?

In August, grass pollen is in season in San Juan — the dominant allergen you're likely reacting to right now. A live count, when available, confirms the day's actual reading; this reflects the typical peak windows for San Juan's warm tropical / sub-tropical climate.

Is tree or grass pollen higher in San Juan in spring?

In San Juan, the tree-versus-grass question is unusual: trees do peak Jan–Apr, but grass never really yields (year-round), so on most spring days BOTH are airborne. A spring bad day here is more often grass than tree, the reverse of colder regions.

What makes San Juan's pollen season distinctive?

San Juan sits in the warm tropical / sub-tropical zone, which means almost no off-season for grass, which pollinates year-round here, so the calendar is less about timing and more about the constant grass baseline. That shapes when symptoms hit and which allergen to watch.

How do I reduce pollen exposure in San Juan?

Through San Juan's peak windows (tree Jan–Apr, grass year-round, ragweed Sep–Nov), 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.

What is the allergy forecast in San Juan today?

The allergy forecast is the airborne-pollen outlook that drives hay fever — exactly what this page tracks. Today's pollen level for San Juan is shown above, broken into the tree, grass, and ragweed pollen behind most seasonal allergies. When the reading is High or Very High, plan for symptoms and pre-medicate; the seasonal calendar below shows which allergen leads in each part of the year.

San Juan, Puerto Rico Pollen Count & Allergy Forecast

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

San Juan, PR · Pollen season

In August, grass pollen is in season in San Juan — the dominant allergen you're likely reacting to right now.

Based on the seasonal pollen calendar for this region.

San Juan on the WeatherStory Allergy Index

San Juan ranks #3 of 100 U.S. metros on the WeatherStory Allergy Index, with a modeled load index of 54 and a 365-day combined pollen season — its heaviest load is grass pollen, running 365 days.

#3of 100

Load index: 54
Combined season: 365 days
Heaviest load: Grass · 365 days

See the full 100 worst U.S. cities for pollen — a modeled seasonal load ranking (see methodology).

Typical now — Augustseasonal estimate, not a live reading

Grass pollen typically leads in San Juan this time of year, at an estimated Moderate level. No live count is wired up; this reflects the seasonal calendar.

Pollen by type this season

TreeOut of seasonpeaks Jan–Apr
GrassIn seasonpeaks year-round
Weed / RagweedOut of seasonpeaks Sep–Nov

What pollinates near San Juan

The tree, grass, and weed species that drive San Juan’s pollen seasons, with each plant’s typical peak.

Trees

Oak Quercuspeaks January–March
Australian pine Casuarinapeaks January–March
Bayberry Myrica ceriferapeaks January–March
Palm Arecaceaepeaks March–May
Melaleuca Melaleuca quinquenerviapeaks October–December

Grasses

Bahia grass Paspalum notatumpeaks April–October
Bermuda grass Cynodon dactylonpeaks March–November
St. Augustine grass Stenotaphrum secundatumpeaks April–October
Johnson grass Sorghum halepensepeaks May–September

Weeds

Ragweed Ambrosiapeaks September–November
Pigweed Amaranthuspeaks September–November
Sedge Cyperuspeaks May–October
Dog fennel Eupatorium capillifoliumpeaks September–November

Species are the region’s common wind-pollinated plants; peak months are a seasonal estimate, not a measured count — see methodology.

San Juan’s allergy year

Typical month-by-month pollen intensity for San Juan, tuned to its latitude and climate region — darker means higher typical counts. The highlighted column is the current month.

JFMAMJJASOND

TreeJan–Dec

Grassyear-round

RagweedSep–Nov

How San Juan compares to the U.S. average

Each colored bar is San Juan’s typical season against the national-average window (grey). The offset is the per-city timing shift.

Tree~13 wks earlier

Grass~22 wks earlier

Ragweed~4 wks later

“U.S. average” is the textbook tree Mar–May, grass May–Jul, ragweed Aug–Oct calendar. The shift is a phenology estimate (Hopkins’ bioclimatic law), not a measured count — see methodology.

How San Juan’s pollen count works

The calendar above is tuned to San Juan’s warm tropical / sub-tropical climate, not a national average: tree pollen runs from week 49 (early December) to week 10 (early March), grass from week 1 (early January) to week 49 (early December), and ragweed from week 36 (early September) to week 44 (early November) here — a 365-day combined pollen season. Those windows are why grass pollen is the one in season in San Juan right now.

No live count is wired up for San Juan today, so the seasonal calendar above is your guide to which allergen is in season. 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 San Juan?: There's barely an off-switch for grass in San Juan — it pollinates year-round, so the usual "three waves" calendar flattens into a near-constant grass baseline. Tree pollen still spikes Jan–Apr and ragweed adds a Sep–Nov layer on top. Currently, grass pollen is what's driving counts this month.
What's in the air in San Juan right now?: In August, grass pollen is in season in San Juan — the dominant allergen you're likely reacting to right now. A live count, when available, confirms the day's actual reading; this reflects the typical peak windows for San Juan's warm tropical / sub-tropical climate.
Is tree or grass pollen higher in San Juan in spring?: In San Juan, the tree-versus-grass question is unusual: trees do peak Jan–Apr, but grass never really yields (year-round), so on most spring days BOTH are airborne. A spring bad day here is more often grass than tree, the reverse of colder regions.
What makes San Juan's pollen season distinctive?: San Juan sits in the warm tropical / sub-tropical zone, which means almost no off-season for grass, which pollinates year-round here, so the calendar is less about timing and more about the constant grass baseline. That shapes when symptoms hit and which allergen to watch.
How do I reduce pollen exposure in San Juan?: Through San Juan's peak windows (tree Jan–Apr, grass year-round, ragweed Sep–Nov), 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.
What is the allergy forecast in San Juan today?: The allergy forecast is the airborne-pollen outlook that drives hay fever — exactly what this page tracks. Today's pollen level for San Juan is shown above, broken into the tree, grass, and ragweed pollen behind most seasonal allergies. When the reading is High or Very High, plan for symptoms and pre-medicate; the seasonal calendar below shows which allergen leads in each part of the year.

Pollen & allergy guides

For the science behind San Juan’s pollen seasons — how counts are measured, when each type peaks, and what the numbers mean — see the pollen & allergy guides.

More for San Juan

See the full San Juan, PR weather forecast — hour-by-hour outlook, NOAA radar, satellite, and air quality.