Explainer
how weather apps work.
How do weather apps get their forecast data?
Weather apps get forecast data primarily from government meteorological services like the National Weather Service and the European Centre for Medium-Range Weather Forecasts. These models process satellite imagery, radar, weather stations, and atmospheric sensors to generate numerical predictions that apps then translate into the forecasts you see on your phone.
the data pipeline
Weather forecasting starts with raw observations: satellite imagery, radar sweeps, weather balloon measurements, ground station readings, and ocean buoys. Government agencies feed this data into numerical weather prediction models that simulate the atmosphere on supercomputers.
These models produce gridded forecasts — temperature, wind, precipitation, humidity, and pressure at every point on a grid covering the globe. Weather apps then query these grids for your location and translate the numbers into the text and icons you see on your phone.
where the data comes from
NWS (GFS)
The National Weather Service Global Forecast System. Free, public, updated four times daily. The backbone of most US weather apps.
ECMWF (ERA5)
The European Centre for Medium-Range Weather Forecasts. Often considered the most accurate global model. Used by premium apps.
Environment Canada (GDPS)
The Canadian Global Deterministic Prediction System. Strong for North American forecasts, less commonly used by US apps.
SunsetWx
Specializes in sunset and sunrise quality forecasting using atmospheric data. Used by Vesper for Sunset Verify predictions.
why most weather apps look identical
Since most weather apps pull from the same data sources, the numbers are nearly identical. What differs is the presentation layer — and most apps use the same approach: template-driven text that fills in variables.
“Partly cloudy. High of 72°F. Winds SW at 5-10 mph.” This sentence exists in some form in nearly every weather app. The template is the same; only the numbers change.
What Vesper does differently
same data, different voice.
Vesper uses the same meteorological sources as other apps. The difference is what happens next. Instead of filling a template, Vesper writes an original editorial brief — short, opinionated, and local.
And with Sunset Verify, Vesper is the only weather app that publicly grades its own predictions. Accuracy verification is rare in weather because it requires admitting when you’re wrong.
Frequently Asked Questions
Do all weather apps use the same data?
Most weather apps pull from the same handful of sources: NWS, ECMWF, and Environment Canada. The data is largely identical — what differs is how each app presents and interprets it.
Why do different weather apps show different temperatures?
Small differences come from which model run an app uses, how often it updates, and whether it applies local corrections or smoothing algorithms.
Why do most weather apps look the same?
Because they use the same data sources and similar template-driven text. Vesper is different because it writes original editorial briefs instead of filling in templates.
How accurate are weather forecasts?
Modern 3-day forecasts are accurate about 80% of the time. Accuracy drops significantly beyond 7 days. Vesper is the only app that publicly tracks and publishes its prediction accuracy for sunsets.
Try the difference