mcp-server-weather

raseniero/mcp-server-weather

3.1

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Weather MCP Server is a lightweight FastMCP service that provides access to National Weather Service alerts and forecasts through simple RPC-style tools.

Weather MCP Server

A lightweight FastMCP service exposing National Weather Service alerts and forecasts via simple RPC-style "tools".

Installation

First, install uv (a fast Python package manager) if you don't have it already:

curl -LsSf https://astral.sh/uv/install.sh | sh

Create virtual environment and activate it

uv venv
source .venv/bin/activate

Install dependencies

uv add "mcp[cli]" httpx

Then install from PyPI:

pip install weather-mcp-server

Or install from source for development:

git clone https://github.com/YourOrg/weather-mcp-server.git
cd weather-mcp-server
pip install -e ".[dev]"

Usage

As a Python library

from weather.nws_client import NWSClient
import asyncio

async def main():
    client = NWSClient()
    alerts = await client.get_alerts("CA")
    for alert in alerts:
        print(alert["headline"], alert["event"], alert["severity"])

asyncio.run(main())

As a FastMCP server

weather-mcp-server --transport stdio

Or

uv run main.py

To run the MCP Inspector:

npx @modelcontextprotocol/inspector

Copy the Session token and the Proxy server address (see example below).

Proxy server listening on 127.0.0.1:6277
Session token: dc7a47f8b6b1a3eede7c507a8d1c9a7f7e6b3ff46c138f8480bbfbae3c45a9e4

Open the MCP Inspector in your browser:http://127.0.0.1:6274, and in the Configuration, paste the values to the following fields below:

Command: uv 
Argument: run main.py
Inspector Proxy Address: http://127.0.0.1:6274
Proxy Session Token: dc7a47f8b6b1a3eede7c507a8d1c9a7f7e6b3ff46c138f8480bbfbae3c45a9e4

API Reference

get_alerts

Fetch formatted weather alerts for a given two-letter US state code.

Arguments:

  • state (str): Two-letter uppercase state abbreviation (e.g. "CA").

Returns:

  • str: Formatted alerts separated by ---, or an error message.

get_forecast

Fetch formatted weather forecast for a location.

Arguments:

  • latitude (float): Latitude between -90 and 90.
  • longitude (float): Longitude between -180 and 180.

Returns:

  • str: Forecast for up to next 5 periods or an error message.

/health

Health check endpoint.

HTTP GET /health

Returns JSON:

  • {"status": "ok"}

Testing & Coverage

  • Tests use pytest, pytest-asyncio, and pytest-cov.
  • Network calls are monkeypatched for isolation in unit tests.
  • Run all tests with: 
    pytest
  • Generate an HTML coverage report with: 
    pytest --cov=src --cov-report=html
open htmlcov/index.html

Fixtures & Mocking

  • Test fixtures and monkeypatching are used to mock NWS API responses and isolate tests from network dependencies.
  • See tests/conftest.py for reusable fixtures.

References