Signal K Virtual Weather Sensors Plugin

A Signal K plugin that fetches weather data from the AccuWeather API and emits it as NMEA2000-compatible Signal K deltas. Provides 24+ environmental data points including temperatures, wind, atmospheric conditions, and marine safety indices.

Features

• 24+ weather data points from AccuWeather: temperatures (7 types), wind (speed, gusts, direction, Beaufort), atmospheric conditions (pressure, humidity, UV, visibility, clouds), and precipitation
• Apparent wind calculation from true wind + vessel motion vectors
• NMEA2000 alignment with signalk-nmea2000-emitter-cannon PGN conventions (130306, 130311, 130312, 130313)
• Interval-based emission (default 5s) for reliable NMEA2000 network recognition
• Delta caching -- only rebuilds the Signal K delta when weather data actually changes
• Rate limit handling with Retry-After header support and linear backoff fallback
• Bounded responses -- 1 MiB cap on AccuWeather response bodies + schema validation before use
• API key sanitization in log output

Installation

From npm

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

Then symlink or copy into your Signal K server's plugin directory:

ln -s "$(pwd)" ~/.signalk/node_modules/signalk-virtual-weather-sensors

Configuration

| Setting | Description | Default | Range | |---------|-------------|---------|-------| | AccuWeather API Key | Required. Get one free at developer.accuweather.com | -- | -- | | Update Frequency | How often to fetch new weather data (minutes) | 5 | 1--60 | | Emission Interval | How often to emit the current data to the NMEA2000 network (seconds) | 5 | 1--60 |

Signal K Paths

Core Environmental

| Path | Unit | Description | |------|------|-------------| | environment.outside.temperature | K | Air temperature | | environment.outside.pressure | Pa | Atmospheric pressure | | environment.outside.humidity | ratio (0--1) | Relative humidity (per Signal K spec) | | environment.outside.dewPointTemperature | K | Dew point | | environment.outside.windChillTemperature | K | Wind chill | | environment.outside.heatIndexTemperature | K | Heat index (RealFeel) |

Enhanced Temperatures

| Path | Unit | Description | |------|------|-------------| | environment.outside.realFeelShade | K | RealFeel in shade | | environment.outside.wetBulbTemperature | K | Wet bulb | | environment.outside.wetBulbGlobeTemperature | K | Wet bulb globe (heat stress) | | environment.outside.apparentTemperature | K | AccuWeather apparent temperature |

Wind

| Path | Unit | Description | |------|------|-------------| | environment.wind.speedTrue | m/s | True wind speed | | environment.wind.directionTrue | rad | True wind direction | | environment.wind.speedOverGround | m/s | Wind speed over ground (mirrors speedTrue) | | environment.wind.speedApparent | m/s | Apparent wind speed (calculated) | | environment.wind.angleApparent | rad | Apparent wind angle relative to bow (omitted when no heading is available) | | environment.wind.speedGust | m/s | Gust speed | | environment.wind.gustFactor | ratio | Gust / sustained ratio | | environment.wind.beaufortScale | 0--12 | Beaufort scale |

Atmospheric & Safety

| Path | Unit | Description | |------|------|-------------| | environment.outside.uvIndex | index | UV radiation (0--15+) | | environment.outside.visibility | m | Visibility distance | | environment.outside.cloudCover | ratio (0--1) | Cloud coverage | | environment.outside.cloudCeiling | m | Cloud base height | | environment.outside.absoluteHumidity | kg/m3 | Calculated absolute humidity | | environment.outside.airDensity | kg/m3 | Calculated air density | | environment.outside.heatStressIndex | 0--4 | Heat stress level | | environment.outside.temperatureDeparture24h | K | 24-hour temperature change | | environment.outside.precipitationLastHour | m | Precipitation in last hour | | environment.outside.precipitationCurrent | m/s | Current precipitation rate |

NMEA2000 Integration

This plugin outputs Signal K deltas only. To bridge them onto a physical NMEA2000 bus, pair with an emitter plugin such as signalk-nmea2000-emitter-cannon. Instance numbers and PGN priority are assigned by the emitter; this plugin does not embed them in the deltas it produces.

PGN Coverage (when paired with signalk-nmea2000-emitter-cannon)

| PGN | Description | Source paths emitted by this plugin | |-----|-------------|-------------------------------------| | 130306 | Wind Data | environment.wind.speedTrue, directionTrue, speedOverGround, speedApparent, angleApparent, speedGust | | 130311 | Environmental Parameters | environment.outside.pressure | | 130312 | Temperature | environment.outside.temperature, dewPointTemperature, windChillTemperature, heatIndexTemperature, realFeelShade, wetBulbTemperature, wetBulbGlobeTemperature, apparentTemperature | | 130313 | Humidity | environment.outside.humidity |

Data Flow

AccuWeather API --> AccuWeatherService (extract + convert to SI units)
                         |
                    WeatherService (add apparent wind from vessel motion)
                         |
                    NMEA2000PathMapper (validate, sanitize, map to SK paths)
                         |
                    index.ts emission timer (emit cached delta every N seconds)
                         |
                    Signal K server --> NMEA2000 emitter --> marine electronics

Development

See DEVELOPMENT.md for full details.

npm run build          # Clean build (types + bundle)
npm run dev            # Watch mode with hot reload
npm run test           # Tests in watch mode
npm run test:run       # Tests once
npm run test:coverage  # Coverage report (80% thresholds)
npm run lint           # Biome check
npm run lint:fix       # Auto-fix
npm run validate       # Type-check + lint + tests (runs on pre-commit)

Tech Stack

• TypeScript 6.0 (strict, ES2023, ESM)
• Node.js 20.18+
• @signalk/server-api 2.24+
• esbuild 0.28 for bundling
• Biome 2.4 for linting/formatting
• Vitest 4.1 for testing (243 tests)
• Husky + lint-staged for pre-commit hooks

License

Apache-2.0 -- see LICENSE.

Contributing

See CONTRIBUTING.md. Pre-commit hooks enforce formatting and tests automatically.

Support

• Report a bug
• Request a feature
• Security issues