fstwthr

fstwthr is a free, keyless weather service at fstwthr.com. It serves the same canonical forecast in seven formats — modern HTML, minimal HTML, plain text, JSON, YAML, wttr.in-style one-liners, and Model Context Protocol for AI agents.

No API keys. No accounts. No advertising. No third-party aggregators. Just government weather data (NOAA in the US, MET Norway globally) shaped into a clean, fast surface.

Try it

curl fstwthr.com/boulder
curl json.fstwthr.com/tokyo
curl 'fstwthr.com/london?units=metric&voice=snark'
curl 'fstwthr.com/denver?format=3'    # wttr.in-style one-liner
curl fstwthr.com/80302          # any US ZIP code

Formats

Query parameters layered on top: ?units=metric for °C/kph/hPa, ?voice=snark|hype for stylistic personality on the summary, ?format=1..4 for one-liners, ?fmt=text|json|yaml|min|modern for explicit format override.

Location lookup

• US cities: /denver, /boulder, /new-york.
• US ZIP codes (33,800 ZCTAs): /80302, /10001.
• Globally famous cities: /london, /paris, /tokyo, /sydney.
• Disambiguate with a region after a comma: /portland,me vs /portland,or; /london,gb vs /london,ky.
• Anywhere OpenStreetMap can find: the long tail resolves via Nominatim and gets KV-cached.

For AI agents

The MCP server at https://mcp.fstwthr.com/mcp exposes eight tools, three resources, and six prompt templates over the same canonical Forecast. Wire it into any MCP-compatible client.

Claude Desktop

// ~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "fstwthr": { "url": "https://mcp.fstwthr.com/mcp" }
  }
}

Cursor / Continue / Cline / Zed / VS Code

All MCP-compatible clients support the same URL-based config — add https://mcp.fstwthr.com/mcp as a server in your settings. See your client's MCP docs for the exact JSON shape.

Tools available

• get_weather(location, units?) — current conditions + short forecast.
• get_forecast(location, days?, units?) — 7-day forecast.
• get_timeline(location, hours?, units?) — next-12-hours hourly outlook.
• get_alerts(location) — active severe-weather alerts.
• get_best_window(location, activity?, units?) — when to be outside (hourly window when available).
• get_activity_weather(location, activity?, units?) — go / caution / avoid for an outdoor activity.
• compare_weather(locations[], units?) — compare 2–4 places and pick the nicest.
• get_nowcast(location) — radar-derived current precipitation (US).

See /llms.txt (short) and /llms-full.txt (long) for the machine-readable description of every surface.

Data sources

• NOAA / National Weather Service — US forecast, alerts, real-time station observations, and radar (MRMS).
• MET Norway / Norwegian Meteorological Institute — global forecast fallback.
• OpenStreetMap Foundation / Nominatim — geocoding for the long tail.
• US Census Bureau Gazetteer — embedded place + ZIP-code data.

All free for non-commercial use. fstwthr passes through attribution in its source field and surfaces no third-party tracking.

Architecture

Single Cloudflare Worker, written in TypeScript with Hono. Every URL is cacheable at the edge (5 min fresh + 1 hour stale-while-revalidate); the upstream JSON is KV-cached separately. Bundle is ~995 KB gzipped including ~50,000 embedded US places + ZIP codes.

A sibling Cloudflare Container parses NOAA MRMS radar tiles every five minutes and writes per-gridpoint "rain on radar" records into shared KV, surfaced to readers as a one-sentence clause in the natural-language summary. That's the heaviest piece of machinery in the project and it still gets out of the way of the main worker entirely.

Contact

Open an issue at github.com/RJFerguson/fstwthr for bug reports, feature requests, or peering interest.