How smoky has the air above your town actually been?

Everyone in fire country has a feeling about this. Nobody has a number. Type a place below and this page will ask NASA for every daily aerosol reading above it since 2015 and count the hazy days while you wait — about a second, no account, nothing sent to us.

Find a place

What it is measuring

Aerosol optical depth: how much of the sunlight heading for a place is intercepted by particles hanging above it. It is a direct measurement of the air column rather than an inference from a drawn plume boundary, and NASA publishes it for every coordinate on earth — which is the only reason one page can answer for Mallacoota, Kelowna and Athens as readily as for a US county.

Every place is scored against its own median. An aerosol depth of 0.15 is a routine afternoon in one town and a genuine event in another, so the only comparison worth making is a place against itself.

What this page was supposed to be, and why it isn't

It started as hours of sunlight lost to wildfire smoke. That number does not survive the data, and the way it fails is instructive. Comparing smoke days with ordinary days across 60 of the most heavily smoked counties in the United States appears to show them 4.1% different in brightness. Control for cloud cover and that collapses to 0.03%. Compare thick smoke against thin, both under clear skies, and you get 1.2%.

The dramatic version was measuring weather. The single darkest day that method turned up — Shasta County, 21 August 2023, apparently 86% below normal — sat under 99.6% cloud. Smoke scatters light forward rather than absorbing it, so the sky goes orange while the energy still arrives. Even the thickest day found here kept 94% of its clear-sky total.

The aerosol, though, is unmistakable: on days NOAA traced a plume overhead, it ran 1.9× the same county's baseline, peaking at 2.39. That is the honest measurement, and it is what the tool above reports.

What it cannot tell you

Aerosol is all airborne particulate. Dust storms, industrial haze, agricultural burning and sea salt all raise it, and nothing here separates them from wildfire smoke. A haze day means the air column was loaded, not that it was smoke.

This is the whole air column, not the air at your window. Particles five kilometres up register exactly the same as particles in your street. For what reached the ground, a monitor is the right instrument — see the Canadian and Australian exceedance layers, which measure what people actually breathed.

NASA's aerosol record runs roughly three months behind, and each value covers a grid cell tens of kilometres across. This describes a region over years, never your street this week.

Where the places come from

18,402 places across 171 countries — 3,839 in Australia, 2,859 in Canada, 5,301 in the United States and 6,403 elsewhere. Names and coordinates come from GeoNames, the open gazetteer, plus the county centroids and monitoring-station sites behind the US smoke-days, Canadian and Australian layers. A coordinate is the only thing this page needs; NASA supplies everything else at the moment you ask.

If your town is not listed, pick the nearest one that is. That is not a workaround — NASA's underlying grid cell is about 55 km across, so a town and its neighbours genuinely return the same numbers. Australian and Canadian coverage runs down to settlements of about 1,000 people; elsewhere it is towns of 25,000 (US) and cities of 100,000 (everywhere else), because below that the extra names would add page weight without adding resolution.

Method and source: NASA POWER daily AOD_55, derived from MERRA-2. Free, keyless, and open to browser requests, which is what makes a lookup like this possible without a server. Place data from GeoNames, used under CC BY 4.0.