open-meteo-mcp-server

Public Hosted Server: https://open-meteo.caseyjhand.com/mcp

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Overview

Global weather from Open-Meteo: forecasts, the historical archive, marine conditions, air quality, probabilistic ensembles, river discharge, and CMIP6 climate projections. Geocode a place name, pull hourly and daily variables for its coordinates, and run SQL over large results staged to DataCanvas. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Tool	Description
openmeteo_search_locations	Resolve a place name to ranked coordinates with country, region, timezone, and population
openmeteo_get_forecast	Current conditions and hourly/daily forecast up to 16 days, with up to 92 past days
openmeteo_get_historical	Hourly/daily history from the reanalysis archive, 1940 to present
openmeteo_get_marine	Wave, swell, and sea-surface conditions: up to 8 forecast days or an archive range
openmeteo_get_air_quality	Modeled CAMS pollutants, pollen, and AQI: current, up to 7 forecast days, or an archive range
openmeteo_get_elevation	Copernicus DEM terrain elevation for up to 100 coordinate pairs
openmeteo_get_ensemble	Per-member ensemble forecast (up to 64 members, up to 35 days) for exceedance and uncertainty
openmeteo_get_flood	GloFAS river discharge forecast (up to 210 days) or reanalysis from 1984
openmeteo_get_climate	Bias-corrected daily CMIP6 projections, 1950–2050, across up to 7 models
openmeteo_dataframe_describe	List the tables and columns staged on a DataCanvas
openmeteo_dataframe_query	Run a read-only SQL SELECT against staged tables
openmeteo_dataframe_drop	Remove one staged table or view from a DataCanvas (opt-in)

Capability reference

openmeteo_search_locations tool

• A bare place name ("Paris", not "Paris, France"), with optional country (ISO 3166-1 alpha-2) and language (default en); count 1–10, default 5
• Each result carries coordinates, an IANA timezone, country / country_code, admin1 / admin2, population, and feature_code; no match fails as no_results
• A notice flags a top match with null or sub-100,000 population, which is what a historic exonym ("Bangalore", "Calcutta") often resolves to
• A native-script query that misses under en is retried once in the language its script implies; when that retry finds the results, effective_language names it (上海 → zh), since their name, country, admin1, and admin2 come back localized in it

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openmeteo_get_forecast tool

• At least one of current_variables, hourly_variables, or daily_variables (up to 50 each); forecast_days 1–16 (default 7), past_days 0–92 (default 0)
• Per-timestamp hourly / daily records with hourly_units / daily_units; current_variables adds a current object from 15-minute data (interval 900) plus current_units
• Prefer past_days over openmeteo_get_historical for the last ~5 days, where the archive's ERA5 components lag

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openmeteo_get_historical tool

• start_date and end_date required (YYYY-MM-DD, from 1940-01-01), plus at least one of hourly_variables / daily_variables, named as on the forecast tool
• Omitting models reads Best Match (IFS HRES + ERA5 + ERA5-Land, source varies by date); up to 8 models pin a source. The ERA5 family runs ~5 days behind, ecmwf_ifs has no delay, and cerra covers Europe only
• Output echoes models and the returned date_range; with 2+ models each column carries a model-name suffix

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openmeteo_get_marine tool

• One window per call: forecast_days 1–8 (upstream default 7) with past_days 0–92, or a start_date / end_date archive range back to at least 2022. Mixing them fails as forecast_window_conflict, a lone date as date_range_incomplete
• At least one of hourly_variables / daily_variables (wave height, period, and direction, swell, sea-surface temperature); sheltered water returns near-zero waves, a land point returns nulls (named in the notice), and ocean_current_velocity is null off the open ocean

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openmeteo_get_air_quality tool

• One window per call: forecast_days 1–7 (upstream default 5) with past_days 0–92, or a start_date / end_date archive range from August 2022 (us_aqi starts a day later). Same forecast_window_conflict and date_range_incomplete rejections as the marine tool
• At least one of current_variables (a current object, interval 3600) or hourly_variables: PM2.5, PM10, NO2, SO2, O3, CO, dust, pollen, European and US AQI. Pollen is modeled for Europe only, in pollen season; elsewhere it comes back null and the notice names it
• data_source: "CAMS" marks every response as modeled grid data, not station measurements

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openmeteo_get_elevation tool

• Parallel latitudes[] / longitudes[] arrays of up to 100 pairs; unequal lengths fail as coordinate_count_mismatch
• elevations[] in input order, each { latitude, longitude, elevation_m } from the Copernicus DEM (~90 m); elevation_m is null where the DEM has no value (latitude 90), without failing the rest of the call

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openmeteo_get_ensemble tool

• At least one of hourly_variables / daily_variables; forecast_days 1–35 (default 7), past_days 0–92. Most models end within 16 days (ncep_gefs05 runs to about day 34); past a model's horizon its columns are null and the notice names where its data ends. models takes one ensemble name (e.g. ecmwf_ifs025_ensemble, 51 members; gem_global_ensemble, 21); omitted or blank, it selects ecmwf_ifs025_ensemble, which the model field echoes
• Each variable returns as per-member columns (temperature_2m_member01, …) across up to 64 members; member_count counts the perturbed members, not the control run
• A regional model queried outside its coverage fails as a non-retryable input error naming the gap; switch to a global model

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openmeteo_get_flood tool

• daily_variables required (up to 20), all in m³/s: river_discharge, the daily discharge value, and the ensemble statistics river_discharge_mean / _median / _min / _max / _p25 / _p75. The statistics exist in forecast mode only; in reanalysis mode they repeat river_discharge and carry no spread
• One mode per call: forecast_days 1–210, or a start_date / end_date reanalysis range from 1984-01-01. Mixing them fails as forecast_days_conflict, a lone date as date_range_incomplete
• Discharge comes from the largest modeled river within 5 km, not always the closest; vary the coordinate by ~0.1° when a value looks off. Null outside GloFAS coverage

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openmeteo_get_climate tool

• start_date / end_date within 1950-01-01 to 2050-12-31 and daily_variables required (the API is daily-only); up to 7 CMIP6 models, e.g. CMCC_CM2_VHR4, MRI_AGCM3_2_S
• With 2+ models each variable is suffixed with the model name; a single or omitted model returns plain names. A variable a model doesn't carry comes back null

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openmeteo_dataframe_describe tool

• Takes the canvas_id a spilled weather tool returned; lists each table's name, kind, row_count, and columns (name, type, nullability), plus the canvas expires_at
• Fails as canvas_not_enabled when canvas is off, or canvas_not_found when the ID is unknown or past its 24-hour sliding TTL

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openmeteo_dataframe_query tool

• canvas_id plus a read-only SELECT against the staged table_name; rows holds up to 100 leading rows, fewer when wide rows would take the response past its 80,000-character inline ceiling (values are never cut). row_count is the exact total, so continue at OFFSET <rows.length>, under an ORDER BY for a stable order
• If counting the full result fails or runs past 5 seconds, the rows still return, row_count is a lower bound, and count_error names the reason (e.g. count_timeout)
• Fails as canvas_not_enabled, canvas_not_found, missing_table, system_catalog_access (system catalogs are blocked), or row_too_large (the first row alone exceeds the ceiling: select fewer columns, or shorten values with left(), substr(), or list_slice())

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openmeteo_dataframe_drop tool

• Off by default: listed as disabled until OPENMETEO_DATAFRAME_DROP_ENABLED=true
• canvas_id plus the exact table_name from openmeteo_dataframe_describe; removes that one table or view and returns dropped and the remaining_tables. A name that is not staged returns dropped: false, so a repeated drop is safe
• Fails as canvas_not_enabled, canvas_not_found, or invalid_table_name (not a plain SQL identifier, or a reserved keyword)

Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

Open-Meteo-specific:

• No API key for non-commercial use; commercial use requires Open-Meteo's paid API tier
• Columnar API responses reshaped into per-timestamp records with *_units maps, on the same variable names across forecast and archive
• DataCanvas spillover on the seven weather tools (forecast, historical, marine, air quality, ensemble, flood, climate): with CANVAS_PROVIDER_TYPE=duckdb an over-budget result is staged as a DuckDB table and the response carries canvas_id, table_name, and truncated: true; with the default none it returns a bounded preview and truncated: true
• models on the historical, ensemble, and climate tools is not an allowlist, so a model Open-Meteo adds later works without a server update

Agent-friendly output:

• Location-first workflow: openmeteo_search_locations returns the IANA timezone alongside coordinates, ready for any weather tool's timezone input (default auto)
• Typed rejections: a variable passed under the wrong cadence fails as variable_wrong_cadence before the upstream call, naming the field it belongs in; an over-wide request fails as request_too_large, naming the inputs to narrow; an upstream rate limit fails as rate_limited on every upstream-calling tool, and only Too many concurrent requests, which clears within seconds, is retried first
• Request URLs never appear in error data or in the log records the client receives
• One notice per response for what the data alone won't show: variable names the endpoint doesn't serve, null values from a location or window outside a dataset's coverage, and where spilled rows went

Getting started

Public Hosted Instance

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

{
  "mcpServers": {
    "open-meteo-mcp-server": {
      "type": "streamable-http",
      "url": "https://open-meteo.caseyjhand.com/mcp"
    }
  }
}

Self-Hosted / Local

Add the following to your MCP client configuration file.

{
  "mcpServers": {
    "open-meteo-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/open-meteo-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "open-meteo-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/open-meteo-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "open-meteo-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": ["run", "-i", "--rm", "-e", "MCP_TRANSPORT_TYPE=stdio", "ghcr.io/cyanheads/open-meteo-mcp-server:latest"]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).
• No API key required. Non-commercial use is free and keyless.
• Commercial use requires Open-Meteo's paid API tier.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/open-meteo-mcp-server.git

2. Navigate into the directory:

cd open-meteo-mcp-server

3. Install dependencies:

bun install

Configuration

Every variable is optional.

Variable	Description	Default
OPEN_METEO_API_BASE_URL	Forecast and elevation API base URL.	https://api.open-meteo.com
OPEN_METEO_ARCHIVE_BASE_URL	Historical archive API base URL.	https://archive-api.open-meteo.com
OPEN_METEO_MARINE_BASE_URL	Marine API base URL.	https://marine-api.open-meteo.com
OPEN_METEO_AIR_QUALITY_BASE_URL	CAMS air quality API base URL.	https://air-quality-api.open-meteo.com
OPEN_METEO_GEOCODING_BASE_URL	Geocoding API base URL.	https://geocoding-api.open-meteo.com
OPEN_METEO_ENSEMBLE_BASE_URL	Ensemble API base URL.	https://ensemble-api.open-meteo.com
OPEN_METEO_FLOOD_BASE_URL	GloFAS flood API base URL.	https://flood-api.open-meteo.com
OPEN_METEO_CLIMATE_BASE_URL	CMIP6 climate API base URL.	https://climate-api.open-meteo.com
CANVAS_PROVIDER_TYPE	duckdb stages over-budget weather results on a DataCanvas and enables the dataframe tools; none returns a bounded preview.	none
OPENMETEO_DATAFRAME_DROP_ENABLED	true makes openmeteo_dataframe_drop callable; otherwise it is listed as disabled.	false
MCP_TRANSPORT_TYPE	Transport: stdio or http.	stdio
MCP_HTTP_PORT	HTTP server port.	3010
MCP_SESSION_MODE	HTTP session mode: stateless, stateful, or auto.	stateless
MCP_AUTH_MODE	Authentication: none, jwt, or oauth.	none
MCP_LOG_LEVEL	Log level (debug, info, notice, warning, error).	info
LOGS_DIR	Directory for log files (Node.js only).	<project-root>/logs
STORAGE_PROVIDER_TYPE	Storage backend: in-memory, filesystem, supabase, cloudflare-kv/r2/d1.	in-memory
OTEL_ENABLED	Enable OpenTelemetry.	false

See .env.example for the full list of optional overrides.

Running the server

Local development

• Build and run the production version:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:http
  # or
  bun run start:stdio
  

• Run checks and tests:

  bun run devcheck  # Lint, format, typecheck, security
  bun run test      # Vitest test suite
  

Docker

docker build -t open-meteo-mcp-server .
docker run --rm -p 3010:3010 open-meteo-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/open-meteo-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

Project structure

Directory	Purpose
src/index.ts	createApp() entry point — registers tools, initializes the Open-Meteo service and DataCanvas.
src/config	Server-specific environment variable parsing and validation with Zod.
src/mcp-server/tools/definitions	Tool definitions (*.tool.ts), one file per tool.
src/mcp-server/tools	Shared tool helpers — model catalog, cadence validation, columnar reshape, spillover, response notices.
src/services/open-meteo	HTTP client for the Open-Meteo APIs — retry, error classification, coverage-gap rejection.
src/services/canvas-accessor.ts	DataCanvas accessor shared by the spill-capable tools.
tests/	Unit, integration, fuzz, and smoke tests.

Development guide

See CLAUDE.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools in the tools[] array in src/index.ts
• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

Attribution

Weather data by Open-Meteo.com, licensed CC BY 4.0.

Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.