nws-weather-mcp-server

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  <h1>@cyanheads/nws-weather-mcp-server</h1>
  <p><b>Get US weather forecasts, active alerts, and current observations via the National Weather Service API. STDIO or Streamable HTTP.</b>
  <div>7 Tools • 1 Resource</div>
  </p>
</div>

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**Public Hosted Server:** [https://nws.caseyjhand.com/mcp](https://nws.caseyjhand.com/mcp)

</div>

---

## Tools

Seven tools for real-time US weather data:

| Tool | Description |
|:----------|:------------|
| `nws_get_forecast` | 7-day or hourly forecast for coordinates. Resolves NWS grid internally. |
| `nws_search_alerts` | Active weather alerts filtered by area, point, zone, event, severity, urgency, certainty, and status. |
| `nws_get_observations` | Current conditions by coordinates (nearest station) or station ID. |
| `nws_find_stations` | Nearby observation stations sorted by distance with bearing. |
| `nws_list_alert_types` | All valid alert event type names for filter discovery. |
| `nws_get_office_discussion` | Latest narrative product (AFD, HWO, ZFP, SPS) from a Weather Forecast Office. |
| `nws_get_zone_forecast` | Text forecast periods for a public NWS forecast zone. |

### `nws_get_forecast`

Get the weather forecast for a US location.

- Default returns named 12-hour periods (14 total, ~7 days)
- Hourly mode returns 48 one-hour periods per page with dewpoint and humidity — the upstream feed carries ~156, and the pre-page total (`totalCount`, against this page's `shown`) plus a truncation notice are surfaced in the enrichment block
- Pass the returned `nextCursor` back as `cursor` to reach the remaining periods; it is omitted on the last page
- Coordinates resolve to NWS grid internally via `/points` endpoint
- Formatted timestamps use the resolved local time zone
- Returns forecast zone and county zone codes for chaining into `nws_search_alerts`

---

### `nws_search_alerts`

Search active weather alerts with flexible filtering.

- Filter by area (state/territory/marine codes), point (lat,lon), zone, land/marine `region_type`, marine `region` groups, event type, severity, urgency, certainty, or status
- `area`, `point`, `zone`, `region_type`, and `region` are mutually exclusive; specify at most one location filter
- National search when no filters provided
- A filter provided with no usable value — a blank `area`/`point`/`zone`, or an empty `event`/`severity`/`urgency`/`certainty`/`region` array — is rejected rather than dropped, so a search never silently widens to national results
- Each `affectedZones` entry carries its NWS zone `type` (`forecast`, `county`, or `fire`) alongside the `code`, so callers can tell which codes chain into `nws_get_zone_forecast`
- Alerts include the CAP message lifecycle — `sent`, `effective`, `status`, `messageType`, and the prior messages an update `references` — distinct from the hazard's own `onset`/`ends`
- Event matching is case-insensitive and partial, so `"tornado"` matches both watches and warnings
- `status` defaults to live `Actual` alerts, but can be set to `Exercise`, `System`, `Test`, or `Draft`
- Optional `limit` (1–25, default 25) sizes the page; `totalCount` reports the full match count and `shown` the size of this page, with a truncation notice and guidance to narrow filters
- Alerts NWS repeats verbatim within one fetch are collapsed on `id`, so `totalCount` counts distinct alerts and a duplicate never straddles a page boundary
- Pass the returned `nextCursor` back as `cursor` to reach matches beyond the page. Consecutive pages are contiguous within one response only — every call re-fetches `/alerts/active`, and that set changes continuously as alerts are issued and expire
- Validates area, point, and zone locally before the API call — malformed values fail fast as `invalid_area_code`, `invalid_point`, or `invalid_zone` instead of leaking a raw upstream 400

---

### `nws_get_observations`

Current measured conditions from a weather station.

- Look up by coordinates (finds nearest station) or station ID directly
- A blank or whitespace-only `station_id` is rejected rather than dropped, so coordinates never silently answer for a station that was asked for by name
- Coordinate lookups choose the nearest station from the candidates returned by NWS
- Dual-unit display: F/C, mph/km/h, inHg/hPa, mi/km
- Observation timestamps use the station's local time zone when available
- Warns when most measurements are unavailable from a station

---

### `nws_find_stations`

Discover nearby observation stations.

- Sorted by haversine distance from query point
- Returns distance (km) and compass bearing
- Includes zone codes, elevation, time zone
- Optional `limit` (1–50, default 10) sizes the page; `totalCount` reports every station near the point and holds steady across pages, while `shown` is the size of this page
- Pass the returned `nextCursor` back as `cursor` to reach stations beyond the page; it is omitted on the last page
- Useful for finding station IDs for `nws_get_observations`

---

### `nws_list_alert_types`

List all valid NWS alert event type names.

- Returns the full set of event types the NWS API recognizes (e.g., "Tornado Warning", "Heat Advisory")
- Use to discover valid values for the `event` filter in `nws_search_alerts`

---

### `nws_get_office_discussion`

Get the latest narrative product from a Weather Forecast Office (WFO).

- `office`: 3-letter WFO code (e.g., `SEW` for Seattle) — returned as the `office` field by `nws_get_forecast`
- `product_type`: `AFD` (Area Forecast Discussion, default), `HWO` (Hazardous Weather Outlook), `ZFP` (Zone Forecast Product), `SPS` (Special Weather Statement)
- Two-hop fetch: lists products by office/type (newest first), then retrieves full product text
- Returns `productText` plus `issuanceTime`, `issuingOffice`, `productName`, `productCode`, `wmoCollectiveId`
- Unknown office returns a clear error with recovery instructions (the NWS API returns HTTP 200 with an empty list, not a 404)

---

### `nws_get_zone_forecast`

Get the text forecast for a public NWS forecast zone.

- `zone_id`: forecast zone code (e.g., `WAZ315`) — returned by `nws_get_forecast` (`forecastZone`), `nws_find_stations` (`forecastZone` column), and `nws_search_alerts` (the `code` of an `affectedZones` entry with `type: "forecast"`)
- Returns named periods (e.g., "Today", "Tonight", "Monday") with narrative text from local forecasters
- Completes the alert-to-forecast chain: look up alert zones, then retrieve zone forecasts
- County (`XXC###`) and fire zone codes are not supported here — NWS publishes no text forecast for them. They remain valid values for the `zone` filter on `nws_search_alerts`

## Resources

| URI Pattern | Description |
|:------------|:------------|
| `nws://alert-types` | Static list of all valid NWS alert event type names. |

## Features

Built on [`@cyanheads/mcp-ts-core`](https://github.com/cyanheads/mcp-ts-core):

- Declarative tool definitions — single file per tool, framework handles registration and validation
- Unified error handling across all tools
- Pluggable auth (`none`, `jwt`, `oauth`)
- Swappable storage backends: `in-memory`, `filesystem`, `Supabase`, `Cloudflare KV/R2/D1`
- Structured logging with optional OpenTelemetry tracing
- Runs locally (stdio/HTTP) or on Cloudflare Workers from the same codebase

NWS-specific:

- Zero-auth access to the NWS API — no API keys required
- Automatic coordinate-to-grid resolution with caching (1h TTL)
- Request timeouts plus retry/backoff for transient NWS API failures
- Dual-unit display for observations (F/C, mph/km/h, inHg/hPa, mi/km)
- Continental US, Alaska, Hawaii, and US territories coverage

## Getting started

### Public Hosted Instance

A public instance is available at `https://nws.caseyjhand.com/mcp` — no installation required. Point any MCP client at it via Streamable HTTP:

```json
{
  "mcpServers": {
    "nws-weather-mcp-server": {
      "type": "streamable-http",
      "url": "https://nws.caseyjhand.com/mcp"
    }
  }
}