Every sky on this page is reconstructed from real data. The words were written by a human. A few honest footnotes follow.
-
Atmospheric data · clouds, humidity, precipitation
High, mid, and low cloud cover at the hour nearest sunset, plus relative humidity and precipitation. Free, CC-BY-4.0 licensed, no API key required.
-
Air quality · smoke, dust, pollution
PM2.5, PM10, dust, and US AQI. Thresholds are ours; the ratio of PM2.5 to PM10 is used to distinguish combustion smoke from urban particulate. The thresholds are tuned for common cases and may misfire at the extremes.
-
Where the fires were
Geographic and seasonal heuristic
When smoke is detected, the prose names a likely source (Sonora, Quebec, the Amazon, and so on) based on latitude, longitude, and month. This is a guess. If the smoke you were breathing came from somewhere else, the sky was still doing what the prose says.
-
Sunset time and sun angle
NOAA Solar Position formulas · public domain
Computed in the browser. The angle used is the sun's altitude ten minutes before sunset, which is about when the color happens.
-
The physics of color
Simplified Rayleigh + Mie scattering model
This is not a photorealistic simulation. It is an interpretive model, closer to an impressionist painting than a spectrograph. Aerosols shift the horizon redder; shallow sun angles amplify the warming; humidity softens everything. If the real sky was more dramatic than ours, it usually was.
-
Geocoding · your city to coordinates
We try the full input first. If that fails, we extract a qualifier (everything after a comma, or the last word) and use it to filter multiple results — so "Paris, Texas" and "Paris Texas" both correctly resolve to Paris, TX rather than Paris, France. The meta line always shows the matched city so you can confirm which one.
-
The prose
Hand-written · Combinatorial, not generative
Around a hundred sentences written by Matt, assembled by conditions. No LLM writes or rewrites anything at runtime. If a condition isn't covered, the prose stays quiet about it — we'd rather leave a line out than fake one.
-
A sister piece
Since You Arrived asks a similar question about a different thing: what the world did while you were reading a tab. Vol. I of what is now, apparently, a series.