weatherfeeder/API.md

weatherfeeder API (Wire Contract)

This document defines the stable, consumer-facing JSON contract emitted by weatherfeeder sinks.

weatherfeeder emits events encoded as JSON. Each event has:

• an envelope (metadata + schema identifier), and
• a payload whose shape is determined by schema.

Downstream consumers should:

1. parse the event envelope,
2. switch on schema, then
3. decode payload into the matching schema.

---

Event envelope

All events are JSON objects with these fields:

Field	Type	Required	Notes
id	string	yes	Stable event identifier. Treat as opaque.
schema	string	yes	Schema identifier (e.g. weather.observation.v1).
source	string	yes	Provider/source identifier (stable within configuration).
effectiveAt	string (timestamp)	yes	RFC3339Nano timestamp indicating when this event is effective.
payload	object	yes	Schema-specific payload (see below).

Timestamp format

All timestamps are encoded as JSON strings using Go’s time.Time JSON encoding (RFC3339Nano).

Examples:

• "2026-01-17T14:27:00Z"
• "2026-01-17T08:27:00-06:00"

---

Canonical schemas

weatherfeeder emits three canonical domain schemas:

• weather.observation.v1
• weather.forecast.v1
• weather.alert.v1

Each payload is described below using the JSON field names as the contract.

---

Shared conventions

Optional fields

Most non-identity measurements are optional. Optional fields are omitted when unknown (i.e., not present).

Units

Canonical payloads are normalized to metric units:

• Temperature: *C (Celsius)
• Wind speed/gust: *Kmh (kilometers/hour)
• Pressure: *Pa (Pascals)
• Visibility / distance / elevation: *Meters (meters)
• Precipitation amount / snowfall depth: *Mm (millimeters)
• Humidity / cloud cover / PoP: *Percent (0–100)

Float rounding

For readability and stability, weatherfeeder rounds floating-point values in canonical payloads to 2 digits after the decimal during normalization finalization.

WMO condition codes

conditionCode uses the WMO weather interpretation code vocabulary.

• Type: integer
• Unknown/unmappable: -1

Downstream consumers should treat unknown codes as “unknown conditions” rather than failing decoding.

---

Schema: weather.observation.v1

Payload type: WeatherObservation

A WeatherObservation represents a point-in-time observation for a station/location.

Fields

Field	Type	Required	Units / Notes
stationId	string	no	Provider station/location identifier
stationName	string	no	Human name, if available
timestamp	string (timestamp)	yes	Observation time
conditionCode	int	yes	WMO code (-1 for unknown)
conditionText	string	no	Canonical short text (often derived from WMO code)
isDay	bool	no	Day/night hint when available
providerRawDescription	string	no	Provider-specific “evidence” text
textDescription	string	no	Legacy/transitional human text
iconUrl	string	no	Legacy/transitional icon URL
temperatureC	number	no	°C
dewpointC	number	no	°C
windDirectionDegrees	number	no	Degrees (meteorological)
windSpeedKmh	number	no	km/h
windGustKmh	number	no	km/h
barometricPressurePa	number	no	Pa
seaLevelPressurePa	number	no	Pa
visibilityMeters	number	no	meters
relativeHumidityPercent	number	no	percent (0–100)
apparentTemperatureC	number	no	°C
elevationMeters	number	no	meters
rawMessage	string	no	Provider raw message (e.g. METAR), if available
presentWeather	array	no	Provider-specific structured fragments
cloudLayers	array	no	Cloud layers (base + amount)

Nested: cloudLayers[]

Each cloudLayers[] element:

Field	Type	Required	Notes
baseMeters	number	no	Cloud base altitude in meters
amount	string	no	Provider string (e.g. FEW/SCT/BKN/OVC)

Nested: presentWeather[]

Each presentWeather[] element:

Field	Type	Required	Notes
raw	object	no	Provider-specific JSON object

---

Schema: weather.forecast.v1

Payload type: WeatherForecastRun

A WeatherForecastRun is a single issued forecast snapshot for a location and a specific product (hourly / narrative / daily). The run contains an ordered list of forecast periods.

product values

product is one of:

• "hourly"
• "narrative"
• "daily"

Fields

Field	Type	Required	Notes
locationId	string	no	Provider location identifier
locationName	string	no	Human name, if available
issuedAt	string (timestamp)	yes	When this run was generated/issued
updatedAt	string (timestamp)	no	Optional later update time
product	string	yes	"hourly", "narrative", or "daily"
latitude	number	no	Degrees
longitude	number	no	Degrees
elevationMeters	number	no	meters
periods	array	yes	Chronological forecast periods

Nested: periods[] (WeatherForecastPeriod)

A WeatherForecastPeriod is valid for [startTime, endTime).

Field	Type	Required	Units / Notes
startTime	string (timestamp)	yes	Period start
endTime	string (timestamp)	yes	Period end
name	string	no	Human label (often empty for hourly)
isDay	bool	no	Day/night hint
conditionCode	int	yes	WMO code (-1 for unknown)
conditionText	string	no	Canonical short text
providerRawDescription	string	no	Provider-specific “evidence” text
textDescription	string	no	Human-facing short phrase
detailedText	string	no	Longer narrative
iconUrl	string	no	Legacy/transitional
temperatureC	number	no	°C
temperatureCMin	number	no	°C (aggregated products)
temperatureCMax	number	no	°C (aggregated products)
dewpointC	number	no	°C
relativeHumidityPercent	number	no	percent
windDirectionDegrees	number	no	degrees
windSpeedKmh	number	no	km/h
windGustKmh	number	no	km/h
barometricPressurePa	number	no	Pa
visibilityMeters	number	no	meters
apparentTemperatureC	number	no	°C
cloudCoverPercent	number	no	percent
probabilityOfPrecipitationPercent	number	no	percent
precipitationAmountMm	number	no	mm (liquid equivalent)
snowfallDepthMm	number	no	mm
uvIndex	number	no	unitless index

---

Schema: weather.alert.v1

Payload type: WeatherAlertRun

A WeatherAlertRun is a snapshot of active alerts for a location as-of a point in time. A run may contain zero, one, or many alerts.

Fields

Field	Type	Required	Notes
locationId	string	no	Provider location identifier
locationName	string	no	Human name, if available
asOf	string (timestamp)	yes	When the provider asserted this snapshot is current
latitude	number	no	Degrees
longitude	number	no	Degrees
alerts	array	yes	Active alerts (order provider-dependent)

Nested: alerts[] (WeatherAlert)

Field	Type	Required	Notes
id	string	yes	Provider-stable identifier (often a URL/URI)
event	string	no	Classification
headline	string	no	Short headline
severity	string	no	e.g. Extreme/Severe/Moderate/Minor/Unknown
urgency	string	no	e.g. Immediate/Expected/Future/Past/Unknown
certainty	string	no	e.g. Observed/Likely/Possible/Unlikely/Unknown
status	string	no	e.g. Actual/Exercise/Test/System/Unknown
messageType	string	no	e.g. Alert/Update/Cancel
category	string	no	e.g. Met/Geo/Safety/...
response	string	no	e.g. Shelter/Evacuate/Prepare/...
description	string	no	Narrative
instruction	string	no	What to do
sent	string (timestamp)	no	Provider-dependent
effective	string (timestamp)	no	Provider-dependent
onset	string (timestamp)	no	Provider-dependent
expires	string (timestamp)	no	Provider-dependent
areaDescription	string	no	Often a provider string
senderName	string	no	Provenance
references	array	no	Related alert references

Nested: references[] (AlertReference)

Field	Type	Required	Notes
id	string	no	Provider reference ID/URI
identifier	string	no	Provider identifier string, if distinct
sender	string	no	Sender
sent	string (timestamp)	no	Timestamp

---

Compatibility rules

• Consumers must ignore unknown fields.
• Producers (weatherfeeder) prefer additive changes within a schema version.
• Renames/removals/semantic breaks require a schema version bump (weather.*.v2).

---

Examples

Observation event (weather.observation.v1)

{
  "id": "nws:KSTL:2026-01-17T14:00:00Z",
  "schema": "weather.observation.v1",
  "source": "nws_observation",
  "effectiveAt": "2026-01-17T14:00:00Z",
  "payload": {
    "stationId": "KSTL",
    "timestamp": "2026-01-17T14:00:00Z",
    "conditionCode": 1,
    "conditionText": "Mainly Sunny",
    "temperatureC": 3.25,
    "windSpeedKmh": 18.5
  }
}

Forecast event (weather.forecast.v1)

{
  "id": "openmeteo:38.63,-90.20:2026-01-17T13:00:00Z",
  "schema": "weather.forecast.v1",
  "source": "openmeteo_forecast",
  "effectiveAt": "2026-01-17T13:00:00Z",
  "payload": {
    "locationName": "St. Louis, MO",
    "issuedAt": "2026-01-17T13:00:00Z",
    "product": "hourly",
    "latitude": 38.63,
    "longitude": -90.2,
    "periods": [
      {
        "startTime": "2026-01-17T14:00:00Z",
        "endTime": "2026-01-17T15:00:00Z",
        "conditionCode": 2,
        "conditionText": "Partly Cloudy",
        "temperatureC": 3.5,
        "probabilityOfPrecipitationPercent": 10
      }
    ]
  }
}

Alert event (weather.alert.v1)

{
  "id": "nws:alerts:2026-01-17T14:10:00Z",
  "schema": "weather.alert.v1",
  "source": "nws_alerts",
  "effectiveAt": "2026-01-17T14:10:00Z",
  "payload": {
    "asOf": "2026-01-17T14:05:00Z",
    "alerts": [
      {
        "id": "https://api.weather.gov/alerts/abc123",
        "event": "Winter Weather Advisory",
        "headline": "Winter Weather Advisory issued January 17 at 8:05AM CST",
        "severity": "Moderate",
        "description": "Mixed precipitation expected...",
        "expires": "2026-01-18T06:00:00Z"
      }
    ]
  }
}