Weather providers and what they measure

LocalSky pulls weather from two kinds of source: a local station sitting in your yard (or one you own, routed through a vendor cloud) and a cloud weather service that fills the gaps your hardware does not cover. They are not equal, and LocalSky never pretends they are. A real station that you own outranks every cloud service for the readings it actually covers; the cloud is there to fill the rest. This page lays the whole picture out as one wide table so you can read across a provider and see, field by field, exactly what its number really is.

Measured vs Nowcast vs Model vs Forecast

Every cell in the table below is one of a small set of honest words. The number on your dashboard might look the same whether it came from a gauge in your grass or a model grid 9 km away, so LocalSky labels its nature, not just its value:

• Measured: a real instrument reading from a physical station. It can lag and it may not be your exact yard (an official station can be an airport miles away), but it is an actual observation, not a computed estimate.
• Radar: a gauge-corrected radar rain estimate (NOAA MRMS). It is observation grade, not a model forecast: it measures the rain that actually fell on a 1 km cell over your block. The best off-yard rain read short of your own gauge.
• Nowcast: a very-short-range analysis blending live radar and station reports (Pirate Weather in the US and Canada). Only seconds of lag, but it is a grid estimate, not a direct measurement.
• Model: a model or ML estimate of the current conditions. Close to now, but computed, never a direct reading.
• Forecast: a model or ML prediction, never a measurement. This is what every model provider’s rain really is, including Pirate’s: its rain is HRRR and GEFS model output, not radar, even when its temp and wind are a live nowcast.

The headline rule: local stations win for what they cover, and cloud services fill the gaps. A station measures your yard; a cloud service estimates it. When both are present, LocalSky takes the station for the fields it has and reaches for the cloud only where the station is silent.

Legend

The full provider capability matrix

Rows are grouped: local stations first (a real station you own, the only sources that are Measured across the board), then the cloud weather services that fill in when you have no hardware for a given reading.

Provider profiles: liveness, freshness, locality

The matrix above says what each provider covers. This table says what each provider is: how live its number is, how often it refreshes and for how long that number stays good, and how close to your yard it resolves. Every value here is joined straight from the code LocalSky runs, so the guide cannot drift from the app: the identity comes from the honest source catalog (src/sources/cloud_catalog.rs), the refresh cadence is each adapter’s poll interval, and the “good up to” window is the freshness ceiling from src/config/region.rs.

Rows follow the same order as the capability matrix (local stations first, then cloud), but the app presents providers by honesty rank (NWS, then your own cloud station, then radar, then the nowcast and model tiers) while irrigation decisions follow rain-trust rank: a real gauge and radar QPE outrank every model no matter how honestly it labels itself. Both orderings live in the catalog on purpose.

Two rows need a word beyond the cell:

• Pirate Weather splits down the middle. Its temp, humidity, wind, pressure, and UV are a live Nowcast (live radar plus station reports, seconds of lag in the US), but its rain is a Forecast, HRRR and GEFS model output, not radar. Read its wind as live and its rain as a prediction, never the reverse. A free key sharpens the live temp and wind reads, and a real gauge still settles whether rain hit your yard.
• Met.no ranks last for irrigation. It is the only provider that emits no live rain reading at all (emits_current_rain = false) and its probability-of-precipitation is synthesized (pop_is_synthetic = true), the only provider true for either. Its rain is not just a forecast, it is a fabricated probability with no live reading behind it.

How to read it

A few rows reward a second look:

• The local stations (Tempest, Ecowitt) are Measured everywhere. Every cell is your own instrument. This is why a station you own outranks every cloud service for the fields it covers: no cloud cell on this table beats a Measured one. Ecowitt’s coverage is modular (the readings light up as you add the matching sensor), but the gateway is capable of every column.
• The PWS rows (Ambient, Netatmo, La Crosse) are Measured too, just cloud routed. They are your own consumer station reached through the vendor cloud, so every field they report is a real on-site measurement, the same gauge a direct LAN hookup would read. They cover fewer columns than a Tempest because the hardware varies (Netatmo needs the add-on anemometer for wind and has no solar or UV; La Crosse is temp, humidity, wind, and a daily rain total).
• NWS is a real Measured observation, but from the nearest official station, often an airport 5 to 30 miles away. It can simply miss the rain that fell on your yard. It reports a current rain rate but not a running daily total.
• NOAA MRMS is rain only, and it is Radar, not a forecast. It measures the rain that actually fell on a 1 km cell over your block: the best off-yard rain read short of your own gauge. It supplies nothing else.
• Synoptic Data is a real Measured observation, just possibly several miles away. It locates the nearest real observation station and supplies its measured wind, pressure, temperature, and humidity (Measured, but possibly several miles away, like NWS). It supplies no rain reading, and it needs a free token.
• Pirate Weather splits. Its temp, humidity, wind, pressure, and UV are a live Nowcast (live radar plus station reports, seconds of lag in the US), but its rain is a Forecast, HRRR and GEFS model output, not radar. So the same Pirate row is honest-blue for wind and honest-amber for rain. A free key sharpens the live temp and wind reads in the US even though its rain is a forecast, and a real gauge still settles whether rain hit your yard.
• OpenWeather, WeatherKit, Open-Meteo, and Met.no are model providers. Their current readings are Model (a computed estimate of now) and their rain is a Forecast (a prediction). Open-Meteo is the keyless backstop and is the only one of the four that also models solar and a daily rain total; Met.no is the coarsest for a US yard (a roughly 9 km grid) and synthesizes its rain probability rather than modeling it.

Lightning is local only

No cloud service on this table reports lightning. It comes only from a station with a strike sensor (Tempest’s hub or an Ecowitt WS6006). If lightning matters to you, that is a hardware reading, not something a cloud key can buy.

What this means for watering

LocalSky decides whether to skip a run on the most trustworthy rain signal it can find, in this order: a gauge on your own yard, then NOAA MRMS radar QPE, then an NWS station observation, then the nowcast and model providers. The table is why: a Measured or Radar rain cell is a fact about water that fell; a Forecast rain cell is a prediction that can report rain that did not fall or miss a small cell. LocalSky will use a forecast when it is all that is available, but it never labels one “live,” and a real gauge always settles the question.

For the merge mechanics behind this (priority, per-field fallback, and bias-correction against your own station), see Forecast sources and merge. For wiring the hardware that earns the Measured rows, see Weather and soil sensors.