Explainer
how weather apps work.
Most weather apps use the same small set of government forecast models, translated into similar template-driven text. Here is the pipeline from satellite to screen — and where Vesper deliberately diverges from the pattern.
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 satellite imagery and atmospheric modeling.
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.
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.
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.
What is the ECMWF model?
ECMWF is the European Centre for Medium-Range Weather Forecasts, widely regarded as the most accurate global weather model. Many weather apps use ECMWF data for their 3-to-10 day forecasts because it consistently outperforms the American GFS model at medium range. Vesper blends multiple sources including ECMWF and NWS.
Why do weather apps disagree with each other?
Apps can run different model generations, weight different sources, update on different schedules, and apply different smoothing or local-correction algorithms. Even when the underlying data is identical, those processing choices produce slightly different numbers on your screen for the same location at the same time.
Are weather forecasts getting more accurate over time?
Yes, steadily. A 5-day forecast today is roughly as accurate as a 3-day forecast was in the 1980s. Satellite resolution, model compute power, and data assimilation techniques have all improved. What has not improved much is how weather apps communicate that accuracy to users — which is what Vesper is trying to fix with editorial voice.
Why do weather apps show hour-by-hour forecasts 10 days out?
They should not. Hour-by-hour forecasts beyond 48 hours communicate false precision — the underlying model uncertainty is much larger than the cells in the grid suggest. Vesper deliberately avoids showing hour-by-hour cells days out because it would misrepresent how confident the model actually is.
Try Vesper
see the difference yourself.
Join the waitlist and we’ll send your first Vesper Brief the morning the app goes live.