diff --git a/packages/modules/common/configurable_forecast.py b/packages/modules/common/configurable_forecast.py
index 985d3378c0..33b31e535c 100644
--- a/packages/modules/common/configurable_forecast.py
+++ b/packages/modules/common/configurable_forecast.py
@@ -115,6 +115,8 @@ def _get_forecast_data(self):
     def update(self) -> None:
         force_update = self._is_force_update_requested()
         if not force_update and not self._is_update_due():
+            # Heute/Morgen-Split hängt vom Kalendertag ab, daher jeden Zyklus neu berechnen
+            self.store.update()
             return
         try:
             trigger_mode = "manuell" if force_update else "geplant"
diff --git a/packages/modules/common/configurable_forecast_test.py b/packages/modules/common/configurable_forecast_test.py
new file mode 100644
index 0000000000..ca6fc57c1c
--- /dev/null
+++ b/packages/modules/common/configurable_forecast_test.py
@@ -0,0 +1,21 @@
+from unittest.mock import Mock
+
+from modules.common.component_state import ForecastState
+from modules.common.configurable_forecast import ConfigurableForecast
+from modules.forecast.open_meteo.config import OpenMeteoForecast
+
+
+def _make_forecast() -> ConfigurableForecast:
+    # strings=[] -> Konfiguration unvollständig, _is_update_due() bleibt False
+    return ConfigurableForecast(OpenMeteoForecast(), Mock(return_value=Mock(return_value=ForecastState())))
+
+
+def test_store_update_runs_even_when_no_fetch_is_due():
+    forecast = _make_forecast()
+    forecast.store = Mock()
+
+    forecast.update()
+
+    forecast.store.update.assert_called_once()
+    forecast.store.set.assert_not_called()
+    forecast._component_updater.assert_not_called()
diff --git a/packages/modules/common/store/_forecast.py b/packages/modules/common/store/_forecast.py
index 8955c0f4db..35c9fb4d1b 100644
--- a/packages/modules/common/store/_forecast.py
+++ b/packages/modules/common/store/_forecast.py
@@ -34,7 +34,8 @@ def _filter_values_for_date(values: Dict[str, float], target_date) -> Dict[str,
 
 class ForecastValueStore(ValueStore[ForecastState]):
     def __init__(self):
-        pass
+        # erlaubt update() bereits vor dem ersten Abruf
+        self.state = ForecastState()
 
     def set(self, state: ForecastState) -> None:
         self.state = state
diff --git a/packages/modules/common/store/_forecast_test.py b/packages/modules/common/store/_forecast_test.py
new file mode 100644
index 0000000000..52ff788ccc
--- /dev/null
+++ b/packages/modules/common/store/_forecast_test.py
@@ -0,0 +1,98 @@
+import time
+from datetime import datetime
+from typing import Optional as TypingOptional
+from unittest.mock import Mock
+
+import pytest
+
+from control import data
+from control.optional import Optional
+from modules.common.component_state import ForecastState
+from modules.common.store import _forecast
+from modules.common.store._forecast import ForecastValueStore
+
+
+@pytest.fixture(autouse=True)
+def mock_data() -> None:
+    data.data_init(Mock())
+    data.data.optional_data = Optional()
+
+
+def _patch_now(monkeypatch: pytest.MonkeyPatch, fixed_now: datetime) -> None:
+    class FixedDateTime(datetime):
+        @classmethod
+        def now(cls, tz: TypingOptional[object] = None):
+            return fixed_now
+
+    monkeypatch.setattr(_forecast, "datetime", FixedDateTime)
+
+
+def _get() -> _forecast.ForecastValueStore:
+    return data.data.optional_data.data.forecast.get
+
+
+def test_update_splits_by_current_calendar_day(monkeypatch: pytest.MonkeyPatch):
+    _patch_now(monkeypatch, datetime(2026, 10, 20, 8, 0, 0))
+    values = {
+        str(int(datetime(2026, 10, 20, 10, 0, 0).timestamp())): 500.0,
+        str(int(datetime(2026, 10, 21, 10, 0, 0).timestamp())): 700.0,
+    }
+    store = ForecastValueStore()
+    store.set(ForecastState(forecast_values=values, daily_kwh={"2026-10-20": 3.5, "2026-10-21": 4.2}))
+
+    store.update()
+
+    assert data.data.optional_data.data.forecast.get.today_kwh == 3.5
+    assert data.data.optional_data.data.forecast.get.tomorrow_kwh == 4.2
+    assert list(data.data.optional_data.data.forecast.get.today_values.values()) == [500.0]
+    assert list(data.data.optional_data.data.forecast.get.tomorrow_values.values()) == [700.0]
+
+
+def test_update_reruns_split_after_midnight_without_new_fetch(monkeypatch: pytest.MonkeyPatch):
+    # Regression-Test: derselbe (unveränderte) Datensatz muss nach Mitternacht korrekt neu
+    # zugeordnet werden, auch ohne dass zwischenzeitlich ein neuer Abruf stattgefunden hat.
+    values = {
+        str(int(datetime(2026, 10, 20, 10, 0, 0).timestamp())): 500.0,
+        str(int(datetime(2026, 10, 21, 10, 0, 0).timestamp())): 700.0,
+    }
+    daily_kwh = {"2026-10-20": 3.5, "2026-10-21": 4.2}
+    store = ForecastValueStore()
+    store.set(ForecastState(forecast_values=values, daily_kwh=daily_kwh))
+
+    _patch_now(monkeypatch, datetime(2026, 10, 20, 23, 50, 0))
+    store.update()
+    assert data.data.optional_data.data.forecast.get.today_kwh == 3.5
+    assert data.data.optional_data.data.forecast.get.tomorrow_kwh == 4.2
+
+    _patch_now(monkeypatch, datetime(2026, 10, 21, 0, 5, 0))
+    store.update()
+    assert data.data.optional_data.data.forecast.get.today_kwh == 4.2
+    assert data.data.optional_data.data.forecast.get.tomorrow_kwh == 0.0
+
+
+def test_update_safe_before_first_fetch():
+    # ForecastValueStore() muss schon vor dem ersten set() aufrufbar sein (siehe
+    # ConfigurableForecast.update(), das update() auch ohne fälligen Abruf jeden Zyklus ruft)
+    ForecastValueStore().update()
+
+
+def test_dst_transition_does_not_shift_day_boundary(monkeypatch: pytest.MonkeyPatch):
+    # Regression-Test: an Zeitumstellungstagen hat der lokale Tag 23 oder 25 Stunden - die
+    # Kalendertag-Zuordnung darf trotzdem nicht verrutschen.
+    monkeypatch.setenv("TZ", "Europe/Berlin")
+    time.tzset()
+    try:
+        values = {
+            str(int(datetime(2026, 10, 25, 23, 30, 0).timestamp())): 100.0,
+            str(int(datetime(2026, 10, 26, 0, 30, 0).timestamp())): 200.0,
+        }
+        store = ForecastValueStore()
+        store.set(ForecastState(forecast_values=values, daily_kwh={}))
+
+        _patch_now(monkeypatch, datetime(2026, 10, 25, 20, 0, 0))
+        store.update()
+
+        assert list(data.data.optional_data.data.forecast.get.today_values.values()) == [100.0]
+        assert list(data.data.optional_data.data.forecast.get.tomorrow_values.values()) == [200.0]
+    finally:
+        time.tzset()
diff --git a/packages/modules/forecast/open_meteo/forecast.py b/packages/modules/forecast/open_meteo/forecast.py
index b83cb5d0b8..995883165b 100644
--- a/packages/modules/forecast/open_meteo/forecast.py
+++ b/packages/modules/forecast/open_meteo/forecast.py
@@ -9,7 +9,8 @@
 
 from modules.forecast.open_meteo.config import OpenMeteoForecast, OpenMeteoForecastConfiguration
 
-OPEN_METEO_FORECAST_HOURS = 48
+# > 48h, damit "morgen" nach Mitternacht schon vor dem ersten Abruf des neuen Tages vollständig vorliegt
+OPEN_METEO_FORECAST_HOURS = 60
 log = logging.getLogger("forecast")
 
 
diff --git a/packages/modules/forecast/open_meteo/forecast_test.py b/packages/modules/forecast/open_meteo/forecast_test.py
new file mode 100644
index 0000000000..279f5edaf0
--- /dev/null
+++ b/packages/modules/forecast/open_meteo/forecast_test.py
@@ -0,0 +1,33 @@
+from datetime import datetime, timedelta
+from unittest.mock import Mock
+
+from modules.common import req
+from modules.forecast.open_meteo import forecast
+from modules.forecast.open_meteo.config import OpenMeteoForecastConfiguration
+
+
+def test_horizon_covers_full_day_after_tomorrow_from_last_daily_fetch():
+    # bei Abruf um 20 Uhr muss "übermorgen" (= "morgen" direkt nach Mitternacht, vor dem ersten
+    # Abruf des neuen Tages um 5 Uhr) noch vollständig enthalten sein
+    assert forecast.OPEN_METEO_FORECAST_HOURS >= 52
+
+
+def test_fetch_forecast_respects_horizon(monkeypatch):
+    start = datetime(2026, 10, 20, 0, 0, 0)
+    hours = forecast.OPEN_METEO_FORECAST_HOURS + 12
+    times = [(start + timedelta(hours=i)).isoformat() for i in range(hours)]
+    radiation = [100.0] * hours
+    response = Mock()
+    response.json.return_value = {"hourly": {"time": times, "global_tilted_irradiance": radiation}}
+    session = Mock()
+    session.get.return_value = response
+    monkeypatch.setattr(req, "get_http_session", Mock(return_value=session))
+
+    config = OpenMeteoForecastConfiguration(
+        latitude=50.0, longitude=10.0, timezone="Europe/Berlin",
+        strings=[{"name": None, "peak_power_kw": 5.0, "tilt": 30.0, "azimuth": 180.0}],
+    )
+
+    values, _ = forecast.fetch_forecast(config)
+
+    assert len(values) == forecast.OPEN_METEO_FORECAST_HOURS