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Severe Weather Sample

This page provides a complete sample response for a severe weather hazard from the Active Hazards API endpoint. Severe weather hazards encompass a broad category of weather alerts including dense fog warnings, special weather statements, severe thunderstorm warnings, and general severe weather advisories issued by national meteorological services. These alerts may follow the Common Alerting Protocol (CAP) standard or use agency-specific formats such as those from the China Meteorological Administration (CMA).

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Severe Weather-Specific Properties

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Incident Data

The incident.properties object for a severe weather hazard contains standard alert metadata. Key incident properties include:

  • senderName - Issuing agency (e.g., "China Meteorological Administration")

  • headline - Alert headline text (e.g., "Heavy fog — Orange Warning (Level II) for Chongming District...")

  • description - Detailed alert description with forecast information and expected impacts

  • severity - Severity level (e.g., "Severe")

  • urgency - Urgency level (e.g., "Unknown")

  • certainty - Certainty level (e.g., "Unknown")

  • event - Event type name (e.g., "Dense Fog")

  • effective / expires / onset - ISO 8601 timing fields for the alert window

  • msgType - Message type (e.g., "Update")

  • instruction - Recommended actions (may be empty for some alerts)

  • category - Category (e.g., "Met" for meteorological)

  • hazardSeverity - Hazard severity classification (e.g., "WATCH")

  • incidentLocationName - Human-readable location (e.g., "Nantong, Jiangsu, China")

  • headlineDescription - Full descriptive headline combining alert status and forecast details

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Features

The features property contains a GeoJSON FeatureCollection with EXPOSURE_AREA and SMART_ALERT features. For CMA-sourced alerts, features include exposure area polygons with severity levels and exposure level indicators rather than CAP_INFO features. The collection may contain multiple exposure area features at different severity levels (e.g., MODERATE, STRONG).

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Exposure Areas

Severe weather hazards may use multiple exposure levels representing different severity zones:

  • Level 1: Moderate exposure area - outer zone with lower expected impact

  • Level 2: Strong exposure area - core zone with highest expected impact

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Sample Response

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Note: Coordinate arrays have been replaced with [...] for brevity. In actual API responses, these contain complete GeoJSON coordinate arrays. The incident.properties object has been truncated with "..." to show only key fields. The full response includes additional metadata fields. This sample shows a CMA-sourced dense fog alert from China, which uses a different property structure than CAP-based alerts from Environment Canada or BoM. The features collection contains EXPOSURE_AREA features at different severity levels and a SMART_ALERT feature. The description field includes summarized content from multiple active alerts issued across the affected region.

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