diff --git a/README.md b/README.md
index 97f9681..88dc45a 100644
--- a/README.md
+++ b/README.md
@@ -90,4 +90,4 @@ Drop the file under `bot/extensions/` and it will be auto-discovered and loaded
 
 - The file must define an `extension` attribute, or the bot will raise a `RuntimeError` on startup.
 - The extension name passed to `Extension()` should match the module's purpose.
-- Each extension should stay focused on a single feature.
\ No newline at end of file
+- Each extension should stay focused on a single feature.
diff --git a/bot/extensions/weather/__init__.py b/bot/extensions/weather/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/bot/extensions/weather/openweather_service.py b/bot/extensions/weather/openweather_service.py
new file mode 100644
index 0000000..8625336
--- /dev/null
+++ b/bot/extensions/weather/openweather_service.py
@@ -0,0 +1,88 @@
+import logging
+import requests
+
+from collections.abc import Mapping
+from enum import Enum
+from typing import cast
+from typing import NotRequired, TypedDict
+
+logger = logging.getLogger(__name__)
+
+OPENWEATHER_URL = "https://api.openweathermap.org/data/2.5/weather"
+
+
+class WeatherCondition(TypedDict):
+    """OpenWeather condition fields used when formatting a forecast."""
+
+    description: str
+    icon: NotRequired[str]  # TODO: figure out how to render icons
+
+
+class MainPayload(TypedDict):
+    """OpenWeather temperature and atmosphere fields used by the formatter."""
+
+    temp: float
+    feels_like: float
+    temp_min: float
+    temp_max: float
+    pressure: int
+    humidity: int
+
+
+class WeatherPayload(TypedDict):
+    """TypedDict for the weather fields used when formatting a forecast."""
+
+    weather: list[WeatherCondition]
+    main: MainPayload
+    visibility: int | None
+    timestamp: int
+
+
+class WeatherError(Enum):
+    """List of possible errors when fetching weather data."""
+
+    NOT_FOUND = "not_found"
+    UNAVAILABLE = "unavailable"
+
+
+def fetch_weather(
+    api_key: str,
+    city: str,
+) -> WeatherPayload | WeatherError:
+    """Retrieve weather information for the specified city."""
+
+    try:
+        response = requests.get(
+            OPENWEATHER_URL,
+            params={"appid": api_key, "q": city},
+            timeout=10,
+        )
+
+        if response.status_code == 404:
+            return WeatherError.NOT_FOUND
+
+        response.raise_for_status()
+        return _normalize_weather_payload(response.json())
+    except requests.HTTPError as error:
+        logger.warning("Weather API HTTP error for %r: %s", city, error)
+    except (requests.ConnectionError, requests.Timeout) as error:
+        logger.warning("Weather API connection error for %r: %s", city, error)
+    except (KeyError, TypeError, ValueError) as error:
+        logger.warning("Weather API payload error for %r: %s", city, error)
+
+    return WeatherError.UNAVAILABLE
+
+
+def _normalize_weather_payload(payload: object) -> WeatherPayload:
+    raw_payload = cast(Mapping[str, object], payload)
+    timezone = int(cast(int | str, raw_payload.get("timezone", 0)))
+    raw_visibility = raw_payload.get("visibility")
+
+    return {
+        "weather": cast(list[WeatherCondition], raw_payload["weather"]),
+        "main": cast(MainPayload, raw_payload["main"]),
+        "visibility": (
+            int(cast(int | str, raw_visibility)) if raw_visibility is not None else None
+        ),
+        "timestamp": int(cast(int | str, raw_payload["dt"])) + timezone,
+    }
diff --git a/bot/extensions/weather/weather_extension.py b/bot/extensions/weather/weather_extension.py
new file mode 100644
index 0000000..9502c53
--- /dev/null
+++ b/bot/extensions/weather/weather_extension.py
@@ -0,0 +1,49 @@
+from matrix import Context, Extension
+from matrix.errors import CheckError
+from .openweather_service import WeatherError, fetch_weather
+from .weather_helper import format_weather
+
+extension = Extension("weather")
+
+
+def _normalize_city_name(city_parts: tuple[str, ...]) -> str:
+    return " ".join(city_parts).title().strip()
+
+
+def _get_api_key() -> str | None:
+    return extension.bot.config.get("api_key", section="extensions.weather")
+
+
+@extension.check
+async def has_api_key(_ctx: Context) -> bool:
+    return _get_api_key() is not None
+
+
+@extension.error(CheckError)
+async def missing_api_key(ctx: Context, error: CheckError) -> None:
+    if isinstance(error, CheckError):
+        await ctx.reply(
+            "Weather extension is not configured with an API key. "
+            "Please set the api_key in the configuration to use this command."
+        )
+
+
+@extension.command(
+    "weather", description="Show current weather information for a city."
+)
+async def weather(ctx: Context, *city: str) -> None:
+    city_name = _normalize_city_name(city)
+
+    api_key: str | None = _get_api_key()
+    if not api_key:
+        await ctx.reply("Weather is not configured.")
+        return
+
+    result = fetch_weather(api_key, city_name)
+    match result:
+        case WeatherError.NOT_FOUND:
+            await ctx.reply(f"Could not find weather data for {city_name}.")
+        case WeatherError.UNAVAILABLE:
+            await ctx.reply("Weather service is temporarily unavailable.")
+        case _:
+            await ctx.reply(format_weather(city_name, result))
diff --git a/bot/extensions/weather/weather_helper.py b/bot/extensions/weather/weather_helper.py
new file mode 100644
index 0000000..54aca5e
--- /dev/null
+++ b/bot/extensions/weather/weather_helper.py
@@ -0,0 +1,68 @@
+from datetime import UTC, datetime
+from .openweather_service import WeatherPayload
+
+
+def format_weather(city: str, data: WeatherPayload) -> str:
+    current_time = _city_time(data["timestamp"]).strftime("%Y-%m-%d %H:%M")
+    weather = data["weather"][0]
+    main = data["main"]
+
+    visibility_m = data["visibility"]
+    visibility_ft = (
+        f"{round(visibility_m * 3.280839895):,}ft"
+        if visibility_m is not None
+        else "n/a"
+    )
+
+    description = weather["description"].title()
+
+    temperature = _format_temperature(main["temp"])
+    feels_like = _format_temperature(main["feels_like"])
+    temp_min = _format_temperature(main["temp_min"])
+    temp_max = _format_temperature(main["temp_max"])
+
+    humidity = main["humidity"]
+    pressure = main["pressure"]
+    visibility = _format_visibility(visibility_m, visibility_ft)
+
+    return (
+        f"### Weather for {city}\n"
+        f"<pre>"
+        f"{'Local time:':<14} {current_time}\n"
+        f"{'Description:':<14} {description}\n"
+        f"{'Temperature:':<14} {temperature}\n"
+        f"{'- Min:':<14} {temp_min}\n"
+        f"{'- Max:':<14} {temp_max}\n"
+        f"{'Feels like:':<14} {feels_like}\n"
+        f"{'Humidity:':<14} {humidity}%\n"
+        f"{'Pressure:':<14} {pressure:,} hPa\n"
+        f"{'Visibility:':<14} {visibility}\n"
+        f"</pre>"
+    )
+
+
+def _city_time(timestamp: int) -> datetime:
+    """Get the local time for the city from a normalized timestamp."""
+
+    return datetime.fromtimestamp(timestamp, UTC)
+
+
+def _format_visibility(visibility_m: int | None, visibility_ft: str) -> str:
+    if visibility_m is None:
+        return "n/a"
+
+    return f"{visibility_m:,}m | {visibility_ft}"
+
+
+def _format_temperature(kelvin: float) -> str:
+    fahrenheit = _kelvin_to_fahrenheit(kelvin)
+    celsius = _kelvin_to_celsius(kelvin)
+    return f"{fahrenheit:.2f}°F | {celsius:.2f}°C"
+
+
+def _kelvin_to_celsius(kelvin: float) -> float:
+    return kelvin - 273.15
+
+
+def _kelvin_to_fahrenheit(kelvin: float) -> float:
+    return kelvin * 1.8 - 459.67
diff --git a/config/development.yaml b/config/development.yaml
index d0ae638..350b58e 100644
--- a/config/development.yaml
+++ b/config/development.yaml
@@ -14,3 +14,5 @@ bot:
 extensions:
   welcome:
     room: "${ADA_MAIN_ROOM|}"
+  weather:
+    api_key: "${ADA_OPENWEATHER_API_KEY|}"
diff --git a/config/production.yaml b/config/production.yaml
index 4667fe2..78c0a63 100644
--- a/config/production.yaml
+++ b/config/production.yaml
@@ -13,3 +13,5 @@ bot:
 extensions:
   welcome:
     room: "!OaOPoyVKqbmPEcMBbt:matrix.org"
+  weather:
+    api_key: "${ADA_OPENWEATHER_API_KEY|}"
diff --git a/tests/extensions/test_weather_extension.py b/tests/extensions/test_weather_extension.py
new file mode 100644
index 0000000..cc9a481
--- /dev/null
+++ b/tests/extensions/test_weather_extension.py
@@ -0,0 +1,100 @@
+from datetime import UTC, datetime
+from unittest.mock import MagicMock, patch
+
+from bot.extensions.weather.openweather_service import WeatherError, fetch_weather
+from bot.extensions.weather.weather_helper import (
+    _city_time,
+    _format_temperature,
+    _format_visibility,
+    format_weather,
+    _kelvin_to_celsius,
+    _kelvin_to_fahrenheit,
+)
+
+from bot.extensions.weather.weather_extension import _normalize_city_name
+
+
+def test_kelvin_to_celsius() -> None:
+    assert round(_kelvin_to_celsius(273.15), 2) == 0
+
+
+def test_kelvin_to_fahrenheit() -> None:
+    assert round(_kelvin_to_fahrenheit(273.15), 2) == 32
+
+
+def test_format_temperature() -> None:
+    assert _format_temperature(273.15) == "32.00°F | 0.00°C"
+
+
+def test_format_visibility_handles_missing_value() -> None:
+    assert _format_visibility(None, "n/a") == "n/a"
+
+
+def test_normalize_city_name_preserves_multiword_city() -> None:
+    assert _normalize_city_name(("los", "angeles")) == "Los Angeles"
+
+
+def test_city_time_uses_timestamp() -> None:
+    assert _city_time(0) == datetime.fromtimestamp(0, UTC)
+
+
+def test_fetch_weather_normalizes_openweather_payload() -> None:
+    fake_response = MagicMock()
+    fake_response.status_code = 200
+    fake_response.json.return_value = {
+        "dt": 1000,
+        "timezone": 3600,
+        "visibility": 10000,
+        "weather": [{"description": "clear sky", "icon": "01d"}],
+        "main": {
+            "temp": 293.15,
+            "feels_like": 294.15,
+            "temp_min": 292.15,
+            "temp_max": 295.15,
+            "humidity": 52,
+            "pressure": 1014,
+        },
+    }
+
+    with patch(
+        "bot.extensions.weather.openweather_service.requests.get",
+        return_value=fake_response,
+    ):
+        result = fetch_weather("api-key", "Paris")
+
+    assert not isinstance(result, WeatherError)
+    assert result["timestamp"] == 4600
+    assert result["visibility"] == 10000
+
+
+def test_format_weather() -> None:
+    message = format_weather(
+        "Paris",
+        {
+            "timestamp": 0,
+            "visibility": 10000,
+            "weather": [{"description": "clear sky", "icon": "01d"}],
+            "main": {
+                "temp": 293.15,
+                "feels_like": 294.15,
+                "temp_min": 292.15,
+                "temp_max": 295.15,
+                "humidity": 52,
+                "pressure": 1014,
+            },
+        },
+    )
+
+    lines = message.splitlines()
+
+    assert lines[0] == "### Weather for Paris"
+    assert lines[1] == "<pre>Local time:    1970-01-01 00:00"
+    assert lines[2] == "Description:   Clear Sky"
+    assert lines[3] == "Temperature:   68.00°F | 20.00°C"
+    assert lines[4] == "- Min:         66.20°F | 19.00°C"
+    assert lines[5] == "- Max:         71.60°F | 22.00°C"
+    assert lines[6] == "Feels like:    69.80°F | 21.00°C"
+    assert lines[7] == "Humidity:      52%"
+    assert lines[8] == "Pressure:      1,014 hPa"
+    assert lines[9] == "Visibility:    10,000m | 32,808ft"
+    assert lines[10] == "</pre>"