Virtual Weather Sensors

A virtual weather station for Signal K: it fetches weather conditions for the vessel's current position and publishes them as 30+ Signal K environment deltas, with severe-weather notifications, a Signal K v2 Weather API forecast provider, and NMEA2000-ready path alignment. It works out of the box with the free, keyless Open-Meteo service; AccuWeather is an optional source for users who have an API key.

The weather data and the notifications are advisory. They are not certified for safety-of-life decisions: always cross-check official forecasts and warnings against your primary instruments.

What's new in 1.13.0

Shared panel components, more resilient provider failover, durable quota controls, truthful observation freshness, and a current development toolchain. No configuration migration is required.

• The panel now shares the Signal K component system. Configuration uses signalk-nearlcrews-ui 0.3.0 for themes, fields, status, layout, and accessible interactions across desktop and embedded marine displays.
• Merged weather is more resilient. Current observations and forecasts fail over in configured order, stale or time-skewed inputs are excluded, and a quota-limited provider does not block healthy keyless sources.
• Quota use survives restarts. AccuWeather requests are reserved atomically in an exact rolling 24-hour window and persisted in the plugin data directory.
• Marine and atmospheric data fail independently. Each layer has its own refresh schedule and freshness gate, so one outage does not freeze the other.
• Shutdown and diagnostics are safer. Active network work is cancelled, provider registration remains consistent, and sensitive values are redacted from logs, banners, URLs, and panel errors.

See the v1.13.0 changelog entry, or the changelog for the full list.

What it does

Signal K is an open marine data standard that streams a boat's navigation, environment, and AIS data over a single API. Virtual Weather Sensors is a Signal K server plugin that fills the environment branch on boats without a masthead weather station: it polls a weather API (keyless Open-Meteo by default, keyless Met.no, or AccuWeather with a key, or all of them blended in merge mode) for conditions at the vessel's GPS position and emits them as standard Signal K deltas that instrument panels, dashboards, and NMEA2000 bridges consume natively.

Every delta carries a provider $source (open-meteo, met-no, accuweather, or vws-merged), so a boat that later gains a real anemometer or barometer can prefer the physical sensor through Signal K source priorities. Any forecast-capable source registers the plugin as a Signal K v2 Weather API provider, serving hourly and daily forecasts over REST, and every source can raise opt-in severe-weather notifications for wind, visibility, heat, cold, and severe conditions.

Features

• 30+ weather data points. Temperatures, wind, pressure, humidity, UV, visibility, cloud cover, pressure tendency, precipitation type, visibility obstruction, and a plain-language condition summary.
• Spec-compliant Signal K paths. Canonical Signal K 1.8.2 leaves under environment.outside.* and environment.wind.*, with AccuWeather extensions and derived values on a producer-namespaced environment.weather.* branch.
• Signal K v2 Weather API provider. Any forecast-capable source (Open-Meteo, Met.no, or AccuWeather) serves forecasts, current observations, and region-aware severe-weather warnings over REST, so dashboards such as Binnacle can show forecast data.
• Apparent wind calculated from the true wind and the vessel's own motion, published on the producer-namespaced branch so it never displaces a real anemometer.
• Severe-weather notifications (opt-in, off by default) for wind, visibility, heat, cold, and severe conditions, with actionable context in every message.
• Shared Signal K configuration panel built with signalk-nearlcrews-ui, with a live status dashboard, an inline API key test, accessible validation and reordering, unsaved-change tracking, and light, dark, and night-red themes. Older admin UIs retain the JSON-schema form fallback.
• NMEA2000 path alignment for bridging onto a physical bus via a companion emitter plugin.
• Per-provider $source on every delta (open-meteo, met-no, accuweather, vws-merged, or open-meteo-marine), so real onboard sensors can win on source priority.

Screenshots

The configuration panel in the Signal K admin UI, with a live status card showing update count, rolling 24-hour API usage, active alerts, and minutes since the last fetch.

| Status dashboard | Notification toggles | Night-red theme | | --- | --- | --- | | | | |

Requirements

• Signal K server 2.x. The Weather API forecast provider needs a server shipping @signalk/server-api 2.24 or newer; on older 2.x servers the plugin still runs and skips the provider registration.
• Node.js 20.18 or newer.
• No API key for the default Open-Meteo source. An AccuWeather API key from developer.accuweather.com is optional, needed only if you select AccuWeather as the source.
• A GPS position published on navigation.position (the plugin queries the active weather provider for the vessel's current location).
• The configuration panel needs Signal K admin UI 2.27.0 or newer. On older servers the plugin still works and falls back to the standard settings form. The custom panel also requires native CSS @scope, available in Chromium and Edge 118+, Firefox 146+, and Safari 17.4+.

Installation

Install from the Signal K admin UI under Appstore, then Available, or from npm:

cd ~/.signalk
npm install signalk-virtual-weather-sensors

From source:

git clone https://github.com/NearlCrews/signalk-virtual-weather-sensors.git
cd signalk-virtual-weather-sensors
npm install
npm run build
ln -s "$(pwd)" ~/.signalk/node_modules/signalk-virtual-weather-sensors

Configuration

In the Signal K admin UI, open Server, then Plugin Config, find "Virtual Weather Sensors", and enable the plugin.

| Setting | Description | Default | Range | |---------|-------------|---------|-------| | Weather source | Open-Meteo (free, keyless, global), Met.no (free, keyless, global), or AccuWeather (needs a key, adds RealFeel, plain-language text, pressure tendency, and precipitation type). In merge mode this source is the primary that sets source priority and backs forecasts. | Open-Meteo | Open-Meteo, Met.no, or AccuWeather | | Provider mode | Single source, or merge available providers into a synthetic vws-merged source that blends current conditions. | Single source | Single or Merge | | AccuWeather API Key | Required only when the source is AccuWeather. Get a key from AccuWeather. | none | n/a | | Open-Meteo base URL | Optional. Leave blank for the free public service (non-commercial use). Self-hosted or paid users can enter a custom endpoint. | none | n/a | | Emit sea state | Adds a keyless Open-Meteo Marine layer (waves, swell, sea temperature, and current) on environment.water.* and environment.current. Coastal and offshore only. | off | boolean | | Weather Update Frequency | Minutes between weather fetches. With AccuWeather selected, the default 30 makes 48 calls/day, within the default 50/day quota. | 30 | 1 to 60 | | Broadcast Interval | Seconds between cached delta re-emissions for NMEA2000 listeners. The provider observation timestamp is retained. | 5 | 1 to 60 | | Daily API Call Quota | Cap on AccuWeather calls per rolling 24-hour window. 0 disables the cap. Open-Meteo is keyless and uncapped. | 50 | 0 to 1000 | | Severe-weather notifications | Master toggle plus per-category sub-toggles (wind, visibility, heat, cold, severe conditions). | master off, sub-toggles on | boolean |

What it emits

The plugin emits 30+ data points under canonical environment.outside.* and environment.wind.* paths from the Signal K 1.8.2 vocabulary, plus a producer-namespaced environment.weather.* branch for provider extensions and plugin-derived values (Beaufort scale, heat stress, gust factor, and more). Some extension leaves are AccuWeather-only (RealFeel, pressure tendency, precipitation type, visibility obstruction, cloud ceiling, and the 24-hour temperature departure); the keyless sources supply the rest, including the plain-language condition summary. With the sea-state option enabled, a keyless Open-Meteo Marine layer adds waves, swell, and sea temperature on environment.water.* and surface current on environment.current. A one-shot meta delta on start describes units and labels for the non-canonical paths.

See docs/signal-k-paths.md for the full path, PGN, and notification reference.

NMEA2000 integration

This plugin outputs Signal K deltas only. To bridge them onto a physical NMEA2000 bus, pair it with an emitter plugin such as signalk-nmea2000-emitter-cannon, which covers PGNs 130306 (wind), 130312 and 130316 (temperatures), 130313 (humidity), and 130314 (pressure). See docs/signal-k-paths.md for the per-PGN path mapping.

Weather API provider

Any forecast-capable source (Open-Meteo, Met.no, or AccuWeather) registers the plugin as a Signal K v2 Weather API provider, so consumers can pull forecasts over REST instead of subscribing to the delta stream. In merged mode the designated forecast child backs the endpoints:

• GET /signalk/v2/api/weather/forecasts/point returns hourly point forecasts.
• GET /signalk/v2/api/weather/forecasts/daily returns daily forecasts.
• GET /signalk/v2/api/weather/observations returns current conditions for the requested position (with pressure and pressure tendency the forecasts omit).
• GET /signalk/v2/api/weather/warnings returns region-aware severe-weather alerts: NWS active alerts for US waters, Met.no MetAlerts for Norwegian waters (both keyless), and reports unsupported positions outside those regions.

Registering the provider is what makes the server list weather under /signalk/v2/features, which is how dashboards such as Binnacle detect that forecast support is available. Forecasts and observations are mapped to SI units and cached on demand. Under AccuWeather they share the plugin's rolling 24-hour API quota so a polling client cannot exhaust a key; Open-Meteo and Met.no are keyless and uncapped. Warnings are keyless and served independently of that quota. See docs/signal-k-paths.md for the populated field reference.

Notifications

Severe-weather notifications under notifications.environment.* are opt-in and off by default. When enabled, the plugin emits one Signal K notification per hazard band transition (entry and exit) across wind, visibility, heat, cold, and severe-condition categories. Each message packs actionable context (for example Gale-force wind: Bf9 from SW, 19 m/s, gusts 27 m/s, 998 hPa). Bridging to NMEA 2000 Alert PGNs requires the separate signalk-to-nmea2000 plugin. See docs/signal-k-paths.md for the full band, trigger, and message reference.

Troubleshooting

Common issues, shown as a status banner in the admin UI:

• Invalid API key (HTTP 401): re-copy the key from AccuWeather with no surrounding whitespace.
• Rate limit or quota reached (AccuWeather only): raise the update frequency interval or the daily quota; the plugin defaults to 50 calls/day.
• No position available: confirm a GPS source publishes navigation.position in the Data Browser.

See docs/troubleshooting.md for the full guide.

Documentation

• Signal K paths, PGNs, and notifications
• Troubleshooting
• Development guide
• Changelog
• Contributing
• Security policy

Development

This project runs on Node 20.18 or newer and supports @signalk/server-api 2.24 through 2.x. Development uses Node 24.18, npm 11.18, Signal K server API 2.30, and TypeScript 7.

git clone https://github.com/NearlCrews/signalk-virtual-weather-sensors.git
cd signalk-virtual-weather-sensors
npm install          # install dependencies
npm run build        # compile the plugin and bundle the config panel
npm test             # Vitest suite, single run
npm run test:browser # build and test the federated panel in Chromium
npm run type-check   # type-check the plugin and the panel
npm run lint         # code, documentation, and spelling checks
npm run lint:fix     # lint and auto-fix
npm run verify       # full non-browser validation
npm run verify:release # full cross-browser release validation

Run npm run validate before committing. See the development guide for the full workflow, and CONTRIBUTING.md for the pull request process. By taking part you agree to the Code of Conduct.

License

Apache-2.0: see LICENSE for the full text. The software is provided "AS IS", without warranty of any kind. Treat the weather data and the notifications as advisory, and always carry independent means of forecasting and navigation.

Acknowledgments

Virtual Weather Sensors is written and maintained by Nearl Crews.

• Signal K Project for the open marine data standard
• Open-Meteo for the free, keyless weather and marine APIs that back the default source
• Met.no (the Norwegian Meteorological Institute) for the free, keyless Locationforecast and MetAlerts APIs
• AccuWeather for the optional weather API this plugin can poll with a key

Virtual Weather Sensors pairs well with sibling plugins such as signalk-nmea2000-emitter-cannon and signalk-binnacle.

Support

Find this plugin useful? You can support its continued development by buying me a coffee.

• Report a bug
• Request a feature
• Security issues