US weather forecasts, alerts, and observations via @cyanheads/nws-weather-mcp-server — 5 tools, NWS API, US-only

@cyanheads/nws-weather-mcp-server v0.7.6 — US Weather via National Weather Service API

Setup

npm install @cyanheads/nws-weather-mcp-server @modelcontextprotocol/sdk
node node_modules/@cyanheads/nws-weather-mcp-server/dist/index.js  # stdio

No API key or env vars needed. Credential-free. Uses @cyanheads/mcp-ts-core framework (JSON structured logging to stderr).

5 Tools Verified

1. nws_list_alert_types — List all 111 valid NWS alert event type names

{"name": "nws_list_alert_types", "arguments": {}}

Returns: 111 event types (Tornado Warning, Flood Watch, Extreme Heat Watch, Blizzard Warning, etc.). Use to discover valid event filter values for nws_search_alerts.

2. nws_find_stations — Find nearby weather observation stations

{"name": "nws_find_stations", "arguments": {"latitude": 40.7128, "longitude": -73.9857, "limit": 3}}

Returns: Station ID, name, distance, bearing, elevation, timezone, county, zone. Sorted by proximity. NYC resolves to KNYC (Central Park, 8km), KLGA (LaGuardia, 11.6km), KEWR (Newark, 15.9km).

3. nws_get_forecast — Get weather forecast for US location

{"name": "nws_get_forecast", "arguments": {"latitude": 40.7128, "longitude": -73.9857}}
{"name": "nws_get_forecast", "arguments": {"latitude": 40.7128, "longitude": -73.9857, "hourly": true}}

Default: 12-hour named periods (Tonight, Tuesday, Tuesday Night...) with temp, wind, precip%, description. hourly: true: hour-by-hour with humidity and dewpoint. Automatically resolves lat/lon → NWS grid office.

4. nws_get_observations — Current weather conditions

{"name": "nws_get_observations", "arguments": {"latitude": 40.7128, "longitude": -73.9857}}
{"name": "nws_get_observations", "arguments": {"station_id": "KORD"}}

Returns: temperature (°F/°C), dewpoint, humidity, wind (direction + speed mph/kmh), pressure (inHg/hPa/Pa), visibility (mi/km/m), cloud layers, heat index. Accepts coordinates (auto-resolves nearest station) OR direct station_id.

5. nws_search_alerts — Search active weather alerts

{"name": "nws_search_alerts", "arguments": {"area": "CA"}}
{"name": "nws_search_alerts", "arguments": {"severity": ["Extreme"]}}
{"name": "nws_search_alerts", "arguments": {"area": "TX", "severity": ["Severe", "Extreme"]}}
{"name": "nws_search_alerts", "arguments": {"point": "40.7128,-73.9857"}}

Filter by: area (state code), point (lat,lon string), zone, event (exact type), severity (array), urgency, certainty, status. Returns: alert ID, headline, severity, urgency, certainty, affected area/counties/zones, onset/expiry times, issuing office, description.

KEY GOTCHAS

1. ⚠️ `severity` must be an ARRAY — "Extreme" fails with Zod validation error; use ["Extreme"]. Same for urgency and certainty.
2. ⚠️ US-only — Non-US coordinates (e.g., London 51.5074,-0.1278) return clear error: "NWS only covers the US. Provide coordinates within US states, territories, or adjacent marine areas."
3. Alaska is SLOW — Alaska forecast takes ~2.5s vs ~300ms for continental US (remote NWS grid offices).
4. Hawaii works — Resolves to PHNL (Daniel K Inouye International Airport) via HFO grid office.
5. Coordinates resolve to nearest NWS grid — NYC (40.7128,-73.9857) resolves to OKX grid office showing "Hoboken, NJ" as location name (grid cell center, not exact input).
6. `point` filter is a STRING — Format: "40.7128,-73.9857" (comma-separated, no spaces).
7. Observations may have missing fields — Some stations report "Wind: Not available" (SF Downtown SFOC1, O'Hare KORD).
8. Output is beautifully formatted Markdown — Tables for stations, structured sections for forecasts, all units in both imperial and metric.

Performance

• p50: 350ms (network-bound, NWS API)
• First call (alert types): ~365ms
• Station resolution: ~1500ms (two API calls: /points → /stations)
• Forecasts after resolution: ~300ms (cached grid)
• Obse