Alerts

Raindrop ingests Environment and Climate Change Canada’s public alerts: watches, warnings, advisories and statements. They arrive in Common Alerting Protocol (CAP) format and are served as GeoJSON. Only the English text is kept.

GET/api/v1/alerts

Returns a GeoJSON FeatureCollection of alerts. Each feature’s geometry is a MultiPolygon of the affected areas, and its properties describe the alert.

startdatetimequery

If set, returns every stored revision whose validity overlaps start to end. If left out, returns only the current revision of each alert that’s active now.

enddatetimequerydefault now

End of the window. Only used with start.

{
  "type": "Feature",
  "id": "urn:oid:2.49.0.1.124.3374137668.2026",
  "geometry": { "type": "MultiPolygon", "coordinates": [] },
  "properties": {
    "id": "urn:oid:2.49.0.1.124.3374137668.2026",
    "issuer": "Environment Canada",
    "messageType": "Update",
    "status": "Active",
    "alertType": "Advisory",
    "alertColour": "Yellow",
    "alertImpact": "Moderate",
    "alertConfidence": "High",
    "alertHeadline": "FROST - IN EFFECT",
    "event": "frost",
    "effectiveTime": "2026-09-24T13:36:00Z",
    "expiryTime": "2026-09-25T05:36:00Z",
    "eventEndTime": "2026-09-25T14:00:00Z",
    "sent": "2026-09-24T13:36:00Z",
    "riskRanking": 8,
    "coverage": "Gatineau",
    "designationCode": "WZ_96_97_CWTO",
    "previousIds": ["urn:oid:2.49.0.1.124.1371159753.2026"],
    "areas": [
      { "description": "Gatineau", "kind": "Coverage", "threatStatus": "None", "clcCode": "031100", "polygons": [] }
    ]
  }
}

alertTypestring

Statement, Advisory, Watch or Warning.

alertColourstring

ECCC’s colour-coded severity: Yellow, Orange or Red.

alertImpact, alertConfidencestring

Low, Moderate, High, or Extreme (impact) or Very High (confidence).

messageTypestring

Alert for a new alert, Update for a revision, or Cancel.

statusstring

Active, Superseded (replaced by a newer revision), Ended or Cancelled.

previousIdsstring[]

IDs of earlier revisions of this alert, oldest first. Use this to group revisions into one alert.

effectiveTime, expiryTimedatetime

When this revision is valid.

eventEndTimedatetime

When the weather itself is expected to end. It’s usually earlier than expiryTime.

riskRankinginteger

ECCC’s risk ranking. 1 is the highest risk.

areasobject[]

The areas the alert covers. Each has a kind (Coverage for a forecast zone, ThreatArea for a storm polygon), a clcCode for forecast zones, and polygons as {lat, lon} rings. Use the feature geometry for drawing; it’s standard GeoJSON.

stormobject

Storm-based alerts only. The storm’s speedKmh, directionDegrees, centroid point, geometryType (IsolatedCell, Line or Area), observation time, and text descriptions of its position and motion.

Storm-based alerts

ECCC issues some severe thunderstorm and tornado warnings as polygons that follow the storm rather than covering whole forecast zones. A storm-based alert is updated every few minutes as the storm moves. Each update is a new revision with a longer previousIds chain. The alert ends with a final revision whose status is Ended.

When storms merge or split, ECCC ends the old alerts and starts new ones with an empty previousIds. The old and new alerts aren’t linked.

For these alerts, areas holds only the storm polygons (kind: "ThreatArea"), so the feature geometry is the storm itself.

Alert zones

GET/api/v1/alerts/zones

The polygons embedded in CAP alerts are coarse and overlap one another. For a cleaner map, draw Coverage areas from ECCC’s forecast zone boundaries, looked up by each area’s clcCode.

codesstringqueryrequired

Comma-separated zone codes, up to 200. Unknown codes are skipped; fall back to the alert’s own polygons for those.

Returns a GeoJSON FeatureCollection. Each feature’s id is the zone code, and its properties are clcCode, nameEn, nameFr, areaKm2 and centroid. Treat codes as opaque strings: air quality zones use compound codes like 082720-082732.

Zone boundaries rarely change, so cache them. Responses carry an ETag; send it back in If-None-Match to get a 304 when nothing has changed.