Kiawe runs March 20 to September 21. Below: every tracked species, its months, and who published them.
Kiawe pollen typically runs March 20 to September 21 here. In October, the calendar has Grasses in season.Hawaii has little seasonal tree pollen and no frost; National Jewish Health notes Hawaii has grass pollen year round, so grass rather than trees drives the pollen calendar.
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 Hawaii’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.
Windows are climatological typicals for Hawaii as published by the sources on this page. They say when a season normally runs, not how strong any given day is.
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.
March 20 to September 21
Midpoint of the published window falls around June 1; the source does not name a peak.
“Flowering mainly in spring and summer.”
USDA Forest Service, Common Forest Trees of Hawaii (Agriculture Handbook 679, reprinted by UH CTAHR)
Window approximates spring and summer. The handbook documents flowering phenology, not allergy; kiawe is a mesquite relative that dominates the dry lowlands of Hawaii from sea level to about 2000 ft.
January 1 to December 31 (in season now)
“Southern states have grass pollens 10 to 11 months out of the year, and Hawaii has grass pollen year-round.”
National Jewish Health, Know Your Allergy Season
National academic medical center source, not a Hawaii institution; UH CTAHR turf publication TM-12 corroborates by noting frequent seed head formation for common bermudagrass in Hawaii lawns. No endsAtFirstFrost because Hawaii has no frost.
June 1 to August 31
“produces seed heads primarily in summer.”
UH CTAHR Cooperative Extension, Common Lawn Grasses for Hawaii (TM-12)
Window approximates summer per the TM-12 appearance notes for carpetgrass; the publication is a turf guide, not an allergy reference.
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.
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.
Hawaii has no reliable median first frost in the populated lowlands, so the ragweed bar above carries no frost-derived end date: where there is no frost, the constraint that ends ragweed season elsewhere never arrives.
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 Hawaii’s tree pollen season is ahead of or behind schedule this year.
No Spring Index reading for Hawaii. USA-NPN’s Extended Spring Indices anomaly grids cover the conterminous United States only, so there is no early-or-late measurement to show here. The sourced calendar above is unaffected.
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.
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.
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.
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.
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: “Dactylis glomerata - Pink with pollen” by Bob Harvey, CC BY-SA 2.0