diff --git a/tests/unit/test_weather.py b/tests/unit/test_weather.py
new file mode 100644
index 0000000..f55722a
--- /dev/null
+++ b/tests/unit/test_weather.py
@@ -0,0 +1,39 @@
+import time
+from unittest.mock import patch, MagicMock
+from vigilar.detection.weather import WeatherFetcher, _weather_code_to_text
+
+
+def test_get_conditions_returns_dict_on_success():
+    fetcher = WeatherFetcher()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"current": {"temperature_2m": 15.5, "weather_code": 2}}
+    with patch("vigilar.detection.weather.requests.get", return_value=mock_response):
+        result = fetcher.get_conditions(45.0, -85.0)
+    assert result is not None
+    assert result["temperature_c"] == 15.5
+    assert isinstance(result["conditions"], str)
+
+
+def test_get_conditions_returns_none_on_failure():
+    fetcher = WeatherFetcher()
+    with patch("vigilar.detection.weather.requests.get", side_effect=Exception("offline")):
+        result = fetcher.get_conditions(45.0, -85.0)
+    assert result is None
+
+
+def test_get_conditions_caches():
+    fetcher = WeatherFetcher()
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"current": {"temperature_2m": 10.0, "weather_code": 0}}
+    with patch("vigilar.detection.weather.requests.get", return_value=mock_response) as mock_get:
+        fetcher.get_conditions(45.0, -85.0)
+        fetcher.get_conditions(45.0, -85.0)
+        assert mock_get.call_count == 1
+
+
+def test_weather_code_mapping():
+    assert _weather_code_to_text(0) == "Clear sky"
+    assert _weather_code_to_text(61) == "Light rain"
+    assert _weather_code_to_text(999) == "Unknown"
diff --git a/vigilar/detection/weather.py b/vigilar/detection/weather.py
new file mode 100644
index 0000000..0bd1bad
--- /dev/null
+++ b/vigilar/detection/weather.py
@@ -0,0 +1,57 @@
+"""Open-Meteo weather fetcher with in-memory caching."""
+
+import logging
+import time
+
+import requests
+
+log = logging.getLogger(__name__)
+
+_WMO_CODES = {
+    0: "Clear sky", 1: "Mainly clear", 2: "Partly cloudy", 3: "Overcast",
+    45: "Fog", 48: "Depositing rime fog",
+    51: "Light drizzle", 53: "Moderate drizzle", 55: "Dense drizzle",
+    61: "Light rain", 63: "Moderate rain", 65: "Heavy rain",
+    66: "Light freezing rain", 67: "Heavy freezing rain",
+    71: "Light snow", 73: "Moderate snow", 75: "Heavy snow", 77: "Snow grains",
+    80: "Light showers", 81: "Moderate showers", 82: "Violent showers",
+    85: "Light snow showers", 86: "Heavy snow showers",
+    95: "Thunderstorm", 96: "Thunderstorm with light hail", 99: "Thunderstorm with heavy hail",
+}
+
+CACHE_TTL_S = 3600
+
+
+def _weather_code_to_text(code: int) -> str:
+    return _WMO_CODES.get(code, "Unknown")
+
+
+class WeatherFetcher:
+    def __init__(self):
+        self._cache: dict[str, tuple[dict, float]] = {}
+
+    def get_conditions(self, lat: float, lon: float) -> dict | None:
+        cache_key = f"{lat:.2f},{lon:.2f}"
+        if cache_key in self._cache:
+            data, ts = self._cache[cache_key]
+            if time.time() - ts < CACHE_TTL_S:
+                return data
+        try:
+            resp = requests.get(
+                "https://api.open-meteo.com/v1/forecast",
+                params={"latitude": lat, "longitude": lon, "current": "temperature_2m,weather_code"},
+                timeout=10,
+            )
+            if resp.status_code != 200:
+                return None
+            j = resp.json()
+            current = j.get("current", {})
+            result = {
+                "temperature_c": current.get("temperature_2m"),
+                "conditions": _weather_code_to_text(current.get("weather_code", -1)),
+            }
+            self._cache[cache_key] = (result, time.time())
+            return result
+        except Exception:
+            log.debug("Weather fetch failed", exc_info=True)
+            return None