Air Quality in Waipahu, Hawaii — Live
Live readings from PurpleAir sensors across Waipahu — with free alerts when vog or brush-fire smoke moves in.
AQI 1 from 5 PurpleAir sensors · Holding steady · data from PurpleAir
As of , the air quality in Waipahu, Hawaii is AQI 1 — Good and holding steady — with PM2.5 at 0.1 µg/m³, the median of 5 live PurpleAir sensors reading 0 to 1. Canairy's verdict: Breathe easy.
For scale, that PM2.5 reading is below the World Health Organization's 24-hour guideline of 15 µg/m³. The WHO figure is a daily average and this is a live reading, so read it as a sense of magnitude rather than a formal exceedance — a brief spike and a bad day are not the same thing. More on the WHO guidelines
Pollen today in Waipahu: grass pollen is the strongest of the three at a none level, from Google's pollen forecast. Canairy shows the tree, grass and weed forecast beside the air reading on every plan, including the free one.
Free to download · Live data from PurpleAir & public monitors
Live PurpleAir sensor map for Waipahu and Pearl City, Waipio, Royal Kunia, Kapolei. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Waipahu
The sensors Canairy reads in Waipahu agree right now — all 5 sit in the Good band, a 1-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 0.5 mi E | 1 | Good |
| 1.8 mi NNE | 1 | Good |
| 3.1 mi N | 1 | Good |
| 3.7 mi E | 0 | Good |
| 5.8 mi SW | 0 | Good |
Waipahu sits on the dry, leeward Ewa Plain of Oahu, and most days the air here is clean. This side of the island only sees about 16 inches of rain a year — a fraction of what falls on the windward coast a few miles away — because the trade winds drop their moisture on the mountains before they ever reach the Ewa side. What actually moves the needle in Waipahu is dry-season brush fire, burning through the guinea grass that has taken over the old Oahu Sugar Company cane fields since the mill closed in 1995, and every so often vog — volcanic haze carried up from the Big Island when the trade winds stall and reverse into a Kona pattern.
What Canairy does for Waipahu
A clear verdict
Not just a number — a plain-English call for Waipahu: open the windows, or keep them shut.
Smoke alerts
A push or text the moment the air crosses your threshold — and again when it clears.
A heads-up before it's bad
Trend alerts catch the air turning, so you can close up the house before the smoke settles in.
Every place you care about
Home, work, the kids' school — across Waipahu or across the country, on one screen.
Why brush fires, not forest fires, are Waipahu's real fire risk
Waipahu grew up around the Oahu Sugar Company mill, incorporated in 1897 and running until the last harvest in 1995. When plantation agriculture shut down across Hawaii, the fields didn't stay empty — they filled in with guinea grass and other fast-growing, fast-drying non-native grasses that carry fire far more readily than the cane crop ever did. That land-use shift, from managed plantation to unmanaged grassland, is the same pattern statewide fire officials pointed to after the 2023 Maui fires, and it applies just as much to the old cane and pineapple ground around Waipahu, Kunia, and the rest of the Ewa Plain as it does on Maui.
The risk is not hypothetical. Early on the morning of July 28, 2026, a brush fire broke out near Waipio Point Access Road in Waipahu, burning close enough to homes that the Honolulu Fire Department and city emergency management shut down the road from Awalai Street to Cane Haul Road while crews worked it. It was contained and the road reopened before 7 a.m., but responders on scene described the fire as large — a reminder that on the dry Ewa side, a fire can start and spread fast on a quiet weekday morning, not just during a headline-grabbing red-flag event.
When Kona winds bring vog up from the Big Island
Kilauea and the Big Island's other active volcanic vents put out somewhere between 2,000 and 4,000 tons of sulfur dioxide a day. Under Hawaii's normal trade wind pattern, that gas and the vog it forms get pushed southwest, away from Oahu, and pool along the Big Island's own Kona coast. Waipahu's air on an ordinary day has nothing to do with it.
The exception is a Kona wind event — a reversal where southerly winds replace the trades, sometimes for days at a stretch. When that happens, vog can drift north across the entire island chain instead of staying pinned to the Big Island, and Oahu's air can turn hazy with sulfate particles even though nothing is burning anywhere nearby. The state's Interagency Vog Information Dashboard and the Hawaii Short-Term SO2 Advisory are built specifically to track those reversals, because a vog day looks nothing like a brush-fire day on a sensor — it shows up as fine particle pollution with no local ignition at all.
The dry months are the ones to watch
Hawaii's wet season runs roughly October through April, when trade winds bring frequent showers; May through September is the dry season, when trade winds are strongest and most consistent but rainfall drops off almost everywhere, leeward areas most of all. That is also when Hawaii's wildfire agencies describe the islands as entering peak fire season, and leeward Oahu communities — from Waipahu through Kunia to the Waianae Coast — carry the state's highest wildfire exposure because of exactly the dry-grass, low-rainfall combination described above.
None of this means Waipahu's air is bad most of the time — it usually isn't. It means the two events that do move the number here, a nearby brush fire or a Kona-wind vog day, can both develop quickly and don't always look the way people expect smoke to look. Checking the actual sensor reading, rather than judging by whether the sky looks smoky, is the more reliable habit here.
Waipahu air quality FAQ
What is the air quality in Waipahu right now?
As of September 14, 2026 at 5:09 AM PDT, the air quality in Waipahu, Hawaii is AQI 1 — Good — with PM2.5 at 0.1 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why does Waipahu get brush fires?
The fields around Waipahu were sugar cane until the Oahu Sugar Company mill closed in 1995. Since then, fast-drying non-native guinea grass has taken over the old plantation land, and on Oahu's dry leeward side that grass burns easily in the May-through-September dry season. A brush fire near Waipio Point Access Road in Waipahu on July 28, 2026 closed the road and burned close to homes before it was contained.
What is vog, and does it reach Waipahu?
Vog is volcanic smog formed when sulfur dioxide from Big Island volcanoes like Kilauea reacts with sunlight and moisture. Normal trade winds keep it over the Big Island's own Kona coast, but during a Kona wind reversal - when winds blow from the south instead of the usual northeast - vog can drift north over the whole state, including Waipahu, showing up as fine particle pollution even with no fire or smoke in sight.
What the AQI numbers mean
| AQI | Category | What it means for you |
|---|---|---|
| 0–50 | Good | Open the windows. Great for outdoor activity. |
| 51–100 | Moderate | Sensitive groups may want to take it slower outside. |
| 101–150 | Unhealthy for Sensitive Groups | Kids, elderly, and respiratory conditions stay closer to home. |
| 151–200 | Unhealthy | Skip outdoor exercise. Close windows. |
| 201–300 | Very Unhealthy | Limit time outside. N95 if you must go. |
| 301+ | Hazardous | Health emergency. Stay inside, run filtration if you have it. |
Canairy lets you tighten these bands if you’re more sensitive than the EPA default, so an alert can fire before the official category changes. How to read the Air Quality Index
Where these readings come from
The AQI at the top of this page is the median of the 5 curated PurpleAir sensors Canairy tracks in and around Waipahu, with outliers set aside so that one sensor brought indoors — or parked beside a barbecue — cannot set the number for a whole city. Every sensor behind it is listed above with its distance and bearing from the city center. There is no black box here.
In the app, a place you save resolves the same way first. When no neighborhood sensor is reporting it falls back to the nearest EPA AirNow monitor, and anything modeled rather than measured is labelled a regional estimate rather than passed off as a sensor reading. How low-cost sensors compare to regulatory monitors
About Canairy
Canairy is free to download. The free plan covers one saved place with live readings, a plain-English verdict, and push alerts when the air crosses a threshold you choose. Paid plans add more places, faster refreshes, and SMS alerts. It is built by two parents in Sonoma County, California, who got tired of guessing whether it was safe to send the kids outside. Why we built it
Go deeper
Air quality near Waipahu
We watch Waipahu's air. You live your life.
Set your threshold once and get a heads-up only when the air actually changes for you. Free on the App Store & Google Play.