diff --git a/app/api/routes/weather.py b/app/api/routes/weather.py
index 1173599..f1e7980 100644
--- a/app/api/routes/weather.py
+++ b/app/api/routes/weather.py
@@ -1,4 +1,7 @@
-from fastapi import APIRouter
+from datetime import date
+
+from fastapi import APIRouter, Query
+from fastapi.exceptions import RequestValidationError
 
 from app.core.errors.base import AppError
 from app.services.external_apis.weather_api import WeatherAPI
@@ -21,10 +24,10 @@
 
 @router.get("/forecast")
 def get_weather_forecast(
-    latitude: float,
-    longitude: float,
-    start_date: str,
-    end_date: str,
+    latitude: float = Query(..., ge=-90, le=90),
+    longitude: float = Query(..., ge=-180, le=180),
+    start_date: date = Query(...),
+    end_date: date = Query(...),
     fields: str | None = None,
 ):
     """
@@ -33,10 +36,24 @@ def get_weather_forecast(
     Coordinates must be supplied as **decimal degrees** — not degree/minute/second notation. E.g. -122.4194, 37.7749.
     Dates must use the **YYYY-MM-DD** format (ISO 8601).
     """
+    if end_date < start_date:
+        raise RequestValidationError(
+            errors=[
+                {
+                    "loc": ("query", "end_date"),
+                    "msg": "end_date must not be before start_date",
+                    "input": end_date.isoformat(),
+                    "type": "value_error",
+                }
+            ]
+        )
+
     weather_api = WeatherAPI()
     try:
         requested = [f.strip() for f in fields.split(",") if f.strip()] if fields else []
-        weather_data = weather_api.get_weather(latitude, longitude, start_date, end_date, hourly_fields=requested)
+        weather_data = weather_api.get_weather(
+            latitude, longitude, start_date.isoformat(), end_date.isoformat(), hourly_fields=requested
+        )
         return weather_data
     except Exception as e:
         raise AppError(str(e), status_code=500)
\ No newline at end of file
diff --git a/tests/test_api.py b/tests/test_api.py
index 7f36dcc..3088215 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -6,6 +6,8 @@
 
 from uuid import uuid4
 
+import pytest
+
 from sqlmodel import select
 
 from app.api.schemas.enums import InputStatus, InputType
@@ -577,6 +579,62 @@ def fake_whisper(*args, **kwargs):
         assert body["detail"]["received_size_bytes"] == 8
 
 
+# ═══════════════════════════════════════════════════════════════════════════
+# Weather endpoint
+# ═══════════════════════════════════════════════════════════════════════════
+
+class TestWeatherEndpoints:
+
+    WEATHER_URL = f"{API_PREFIX}/weather/forecast"
+    VALID = {"latitude": 37.77, "longitude": -122.42, "start_date": "2026-10-19", "end_date": "2026-10-20"}
+
+    def _no_upstream_call(self, monkeypatch):
+        def fake_get_weather(*args, **kwargs):
+            raise AssertionError("Open-Meteo should not be called for invalid input")
+
+        monkeypatch.setattr(
+            "app.api.routes.weather.WeatherAPI.get_weather", fake_get_weather
+        )
+
+    def test_forecast_valid_request(self, client, monkeypatch):
+        captured = {}
+
+        def fake_get_weather(self, latitude, longitude, start_date, end_date, hourly_fields=None):
+            captured.update(latitude=latitude, longitude=longitude, start_date=start_date, end_date=end_date)
+            return {"hourly": {}}
+
+        monkeypatch.setattr("app.api.routes.weather.WeatherAPI.get_weather", fake_get_weather)
+
+        resp = client.get(self.WEATHER_URL, params=self.VALID)
+        assert resp.status_code == 200
+        assert captured == {
+            "latitude": 37.77,
+            "longitude": -122.42,
+            "start_date": "2026-10-19",
+            "end_date": "2026-10-20",
+        }
+
+    @pytest.mark.parametrize(
+        "overrides, field",
+        [
+            ({"latitude": 200}, "query.latitude"),
+            ({"latitude": -90.5}, "query.latitude"),
+            ({"longitude": 181}, "query.longitude"),
+            ({"start_date": "tomorrow"}, "query.start_date"),
+            ({"end_date": "2026-13-01"}, "query.end_date"),
+            ({"start_date": "2026-10-22", "end_date": "2026-10-19"}, "query.end_date"),
+        ],
+    )
+    def test_forecast_invalid_params_rejected(self, client, monkeypatch, overrides, field):
+        self._no_upstream_call(monkeypatch)
+
+        resp = client.get(self.WEATHER_URL, params={**self.VALID, **overrides})
+        assert resp.status_code == 422
+        body = resp.json()
+        assert body["error_code"] == "VALIDATION_ERROR"
+        assert body["validation_errors"][0]["field"] == field
+
+
 # ═══════════════════════════════════════════════════════════════════════════
 # End-to-end pipeline
 # ═══════════════════════════════════════════════════════════════════════════