New Jersey Pollen Calendar: Season by Species

Q: What pollen is high in October in New Jersey?

Based on the sourced windows on this page, mid October in New Jersey falls inside the season for Ragweed. Whether the air is actually thick with it on a given day depends on weather; the windows say what is possible, not what today's count is.

Q: Where can I check today's pollen count for New Jersey?

Certified daily counts are published by the National Allergy Bureau at pollen.aaaai.org, which lists counting stations run under the American Academy of Allergy, Asthma and Immunology, and search engines print a daily pollen card for most locations. This site publishes the calendar: which species, which months, and the frost date that ends weed season.

Q: Do the New Jersey pollen windows change from year to year?

The published windows are climatological typicals and stay put; the year moves around them. ACAAI notes that "Mild winter temperatures can cause plants to pollinate early." That is exactly why the tree season panel shows the Spring Index anomaly, and why the ragweed end is tied to the first frost rather than to a fixed date.

Q: Where does this data come from, and can I check it?

Yes, and you should. Every species window names its institution and links its page, with the sentence we relied on quoted under the card. The frost medians behind the derived ragweed ends are the NOAA 1991 to 2020 normals in our first frost pages. The Spring Index proxy is read live from the USA National Phenology Network under CC BY 4.0.

Oak runs February 1 to May 31. Below: every tracked species, its months, and who published them.

Oak pollen typically runs February 1 to May 31 here. In October, the calendar has Ragweed in season.

Oak season

Feb 1 to May 31

In season this October

Sourced windows

Where the New Jersey pollen year stands

Climatological windows, resolved against today

Weed

groups in season, mid October

Ragweed

Feb 1 to May 31

oak season

per Maryland Department of Health (pollen indicator)

October 20

median first frost

the date that ends ragweed season here (derived)

Rutgers has monitored ragweed onset in the New York - New Jersey metro area and reports the season has grown longer over the past 20 years (https://www.rutgers.edu/news/first-ragweed-season-sighted-new-jersey-and-new-york, fetched 2026-08-27).

The calendar

What pollinates when in New Jersey

Every bar is a sourced season window; the institution and sentence behind each one are printed in the species cards below. Bars marked ❄ end at New Jersey’s median first frost, a date we compute from NOAA normals rather than copy from a source, because frost is what physically stops frost-tender weeds like ragweed.

OakTreeFebruary 1 to May 31

GrassesGrassMay 1 to August 31

RagweedWeedAugust 21 to October 20 ❄ derived

trees grasses weeds today❄ end derived from median first frost

Windows are climatological typicals for New Jersey as published by the sources on this page. They say when a season normally runs, not how strong any given day is.

Birch branch with hanging catkins and fresh spring leaves over a green field — The species that leads a state’s calendar decides when its worst weeks land, which is why every state page opens with different months. “New leaves and catkins on a birch at Mystigen 2” by W.carter, CC BY-SA 4.0

Species by species

The windows, with their sources

Each card shows the months, the institution that published them, and the verbatim sentence the window came from. Where a date is computed by us rather than published, the card says so in as many words.

OakTree

Quercus spp.

February 1 to May 31

“In Maryland and in other states in the mid-Atlantic region pollen spores are produced by different sources that include trees in late winter and spring, different types of grasses in spring and summer and various weed types in late summer and fall of each year.”

Maryland Department of Health (pollen indicator)

The quote explicitly covers mid-Atlantic states, which includes New Jersey; late winter mapped to Feb 1 and spring end to May 31. Window covers total tree pollen, not oak alone. Rutgers NJAES separately reported that in New Jersey "tree pollen counts recorded in April this year were the highest in the past 25 years" (https://sebsnjaesnews.rutgers.edu/2013/08/study-reveals-longer-and-overlapping-pollen-seasons-related-to-seasonal-warming/, fetched 2026-08-27), consistent with an April peak.

GrassesGrass

Poaceae (timothy, Kentucky bluegrass)

May 1 to August 31

The source puts the peak around June 15.

“Pollen levels increase from May through August, peaking in June.”

Penn State Extension

Window published by Penn State Extension for its region; used for adjacent New Jersey. Rutgers NJAES adds a New Jersey twist: "The grass pollen release has lasted longer and is even projected to recur in September when a second grass pollen season during "Indian summer" is common." (https://sebsnjaesnews.rutgers.edu/2013/08/study-reveals-longer-and-overlapping-pollen-seasons-related-to-seasonal-warming/, fetched 2026-08-27).

RagweedWeed

Ambrosia artemisiifolia

August 21 to October 20 ❄ end derived from median first frost (in season now)

“sightings of ragweed generally occur towards the end of the third week of August”

Rutgers University (Center for Environmental Prediction ragweed reporting) · end date computed by us from NOAA 1991 to 2020 frost normals, not published by the source

Companion Rutgers NJAES reporting: "We normally see ragweed pollinate at the end of August, but can expect it around August 10-15 this year and earlier if we have a dry spell" (https://sebsnjaesnews.rutgers.edu/2013/08/study-reveals-longer-and-overlapping-pollen-seasons-related-to-seasonal-warming/, fetched 2026-08-27). The same Rutgers article ties the season end to first frost timing: "As global average temperatures have warmed, the first frost has been delayed, especially at higher latitudes".

What the allergy bodies say, in their words. AAAAI: “Seasonal allergic rhinitis is often caused by tree pollen in the early spring. During the late spring and early summer, grass pollen often cause symptoms. Late summer and fall hay fever is caused by weed pollen.” ACAAI: “Tree pollination begins earliest in the year followed by grass pollination later in the spring and summer and ragweed in the late summer and fall.” For anything about symptoms or treatment, see a clinician.

The frost connection

Why ragweed season in New Jersey ends on a frost date

Ragweed is a short-day annual: it starts shedding pollen as days shorten in late summer and keeps going until cold kills it. The US EPA’s technical documentation for its ragweed pollen indicator puts it plainly: the season “ends in response to cold weather in the fall (i.e., first frost)”, and ragweed “will not continue flowering once temperatures dip below freezing.” EPA’s own analysis truncates every station’s ragweed season at the first fall frost.

This page derives the end date from that rule: New Jersey's median first fall frost is October 20 (NOAA 1991 to 2020 normals, the same number our first frost pages publish), and that is the derived end date on the ragweed bar above. It is a median: about half of years frost earlier, half later, and EPA's indicator work shows fall frosts arriving later than they used to across the northern states, which is exactly why ragweed seasons have been getting longer.

Common ragweed flower spike held upright against a clear blue sky — Common ragweed in flower. Each spike sheds wind-borne pollen from late summer until the plant is killed by freezing temperatures, which is why the end of its season is a frost statistic rather than a botany fact. “Ambrosia artemisiifolia flowerhead7” by Harry Rose, CC BY 2.0

Live proxy · USA-NPN

Is tree season running early or late in New Jersey?

USA-NPN’s Extended Spring Indices measure how early or late spring leaf-out and bloom are running against the 1991 to 2020 normal. The index knows nothing about pollen; it tracks cloned lilacs and honeysuckles. But wind-pollinated trees flower in the same early-spring window it measures, so it is a usable, clearly labelled proxy for whether New Jersey’s tree pollen season is ahead of or behind schedule this year.

First Leaf Index

…

Leaf-out of lilacs and honeysuckles, the earliest woody plants to break bud.

First Bloom Index

…

Flowering of lilacs and honeysuckles, which USA-NPN associates with blooming of early-spring shrubs and leaf out of deciduous trees.

What this is

A proxy, stated as one. The index tracks lilac and honeysuckle leaf-out and bloom, not pollen. Wind-pollinated trees flower in the same early-spring window, so an early index spring usually means an early tree pollen season. It says nothing about grass or ragweed.

The live grid currently holds the finished spring of 2026, shown as history. Tree windows above are not shifted by it; readings for the coming spring start filling in from late January.

Pine branch with yellow pollen cones releasing a visible cloud of pollen into the wind — A pine shedding pollen into the wind. Wind-pollinated trees release enormous quantities because almost none of it lands on another flower, which is also why it lands on everything else. “Pine releasing pollen into the wind in Tuntorp 1” by W.carter, CC BY-SA 4.0

How this page is built

A calendar, not a count

Sourced windows

Every season window names the extension service, agency or university that published it, with the sentence quoted on the card. Where nobody publishes a window, the page says so instead of inventing one.

Derived ragweed ends

Weed bars marked with the frost symbol end on the state’s median first frost, computed from NOAA 1991 to 2020 normals and labelled as derived, on the strength of EPA’s ragweed indicator documentation.

A labelled proxy, not a forecast

The Spring Index anomaly is a measurement of the spring that has already run. It shifts nothing except spring tree windows, and only while the year’s spring is actually in progress.

No counts, by design

Daily counts belong to the certified counting stations of the National Allergy Bureau, and search engines already print them. This site publishes the part nobody prints: the calendar.

Common questions

New Jersey pollen season FAQ

When is oak pollen season in New Jersey?

Maryland Department of Health (pollen indicator) supports a window of roughly February 1 to May 31. Their words: "In Maryland and in other states in the mid-Atlantic region pollen spores are produced by different sources that include trees in late winter and spring, different types of grasses in spring and summer and various weed types in late summer and fall of each year." That is a climatological typical, not a forecast; any single year commonly runs a week or two either side of it.

When does ragweed season start and end in New Jersey?

The start comes from the source on the card. The end is different: we compute it from New Jersey's median first fall frost, October 20, because the US EPA's ragweed indicator documentation states that ragweed pollen season "ends in response to cold weather in the fall (i.e., first frost)" and that ragweed "will not continue flowering once temperatures dip below freezing." The end date is therefore derived by us from NOAA 1991 to 2020 frost normals, and the page labels it that way. A late first frost stretches the season; an early one cuts it short.

What pollen is high in October in New Jersey?

Is pollen season early or late this year?

For spring tree pollen there is a usable proxy. USA-NPN's Extended Spring Indices measure how early or late spring leaf-out and bloom are running against the 1991 to 2020 normal, at 4 km resolution, updated daily. Wind-pollinated trees flower in that same early spring window, so an early index spring usually means an early tree pollen season. It is a proxy and this page labels it as one: the index models lilacs and honeysuckles, not pollen, and it says nothing about grass or ragweed timing.

Where can I check today's pollen count for New Jersey?

What do the allergy organizations say about pollen exposure?

The allergy societies publish the practical guidance. AAAAI: "Keep your windows closed at home and if possible, use air conditioning, which cleans, cools and dries the air." AAAAI: "Pollen tends to travel more with hot, dry and windy weather, which can increase your allergy symptoms." ACAAI: "Take a shower, wash your hair and change your clothes after you've been working or playing outdoors." For anything about symptoms or treatment, talk to a clinician.

Do the New Jersey pollen windows change from year to year?

Where does this data come from, and can I check it?

Orchard grass flower heads with pink anthers spread for wind pollination — Orchard grass in flower, anthers out. Grass pollen is the midsummer act of the calendar almost everywhere, and a lawn kept mowed never reaches this stage, which is the whole connection to the mowing schedule. “Dactylis glomerata - Pink with pollen” by Bob Harvey, CC BY-SA 2.0

The rest of the New Jersey calendar

Plan around the New Jersey seasons

New Jersey frost datesThe median first frost is the date that ends ragweed season here. Same number, two pages.Spring bloom timingThe same Spring Index that flags an early tree pollen year also moves the wildflower calendar.New Jersey lawn calendarGrass pollen comes from grass allowed to flower. The mowing calendar is the other half of that story.

More Northeast pollen calendars

Season windows are climatological typicals, each attributed on its card to the institution that published it, with the supporting sentence quoted. Frost-derived weed season ends are computed by us from NOAA 1991 to 2020 median first frost dates and labelled as derived wherever they appear; the frost link is documented by the US EPA’s ragweed pollen indicator technical documentation. Spring Index anomalies are read live in your browser from the USA National Phenology Network (www.usanpn.org, CC BY 4.0) and shown as a labelled proxy for spring tree pollen timing. National picture: every state’s pollen calendar →
Hero image: “New leaves and catkins on a birch at Mystigen 2” by W.carter, CC BY-SA 4.0