diff --git a/climada/util/forecast.py b/climada/util/forecast.py
index 84225c47fe..1fbd090db9 100644
--- a/climada/util/forecast.py
+++ b/climada/util/forecast.py
@@ -19,6 +19,40 @@
 Define Forecast base class.
 """
 
+import numpy as np
+
 
 class Forecast:
-    pass
+    """Mixin class for forecast data.
+
+    Attributes
+    ----------
+    lead_time : np.ndarray
+        Array of forecast lead times, given as datetime64 objects.
+        Represents the time points for which forecasts are made.
+    member : np.ndarray
+        Array of ensemble member identifiers, given as integers.
+        Represents different forecast ensemble members.
+    """
+
+    def __init__(
+        self,
+        lead_time: np.ndarray | None = None,
+        member: np.ndarray | None = None,
+        **kwargs,
+    ):
+        """Initialize Forecast.
+
+        Parameters
+        ----------
+        lead_time : np.ndarray or None, optional
+            Forecast lead times. Default is empty array.
+        member : np.ndarray or None, optional
+            Ensemble member identifiers. Default is empty array.
+        """
+
+        self.lead_time = (
+            np.asarray(lead_time) if lead_time is not None else np.array([])
+        )
+        self.member = np.asarray(member) if member is not None else np.array([])
+        super().__init__(**kwargs)
diff --git a/climada/util/test/test_forecast.py b/climada/util/test/test_forecast.py
index 196573e583..f500c4ba88 100644
--- a/climada/util/test/test_forecast.py
+++ b/climada/util/test/test_forecast.py
@@ -18,3 +18,35 @@
 
 Tests for Forecast base class.
 """
+
+import numpy as np
+import numpy.testing as npt
+
+from climada.util.forecast import Forecast
+
+
+def test_forecast_init():
+    """Test initialization of Forecast class."""
+    forecast = Forecast()
+    npt.assert_array_equal(forecast.lead_time, np.array([]))
+    npt.assert_array_equal(forecast.member, np.array([]))
+
+    forecast = Forecast(member=np.array([1, 2]))
+    npt.assert_array_equal(forecast.member, np.array([1, 2]), strict=True)
+
+    forecast = Forecast(lead_time=np.array([1, 2]))
+    npt.assert_array_equal(forecast.lead_time, np.array([1, 2]), strict=True)
+
+    forecast = Forecast(lead_time=np.array([1, 2]), member=[3, 4])
+    npt.assert_array_equal(forecast.lead_time, np.array([1, 2]), strict=True)
+    npt.assert_array_equal(forecast.member, np.array([3, 4]), strict=True)
+    assert isinstance(forecast.member, np.ndarray)
+
+    # Test with datetime64 including seconds
+    lead_times_seconds = np.array(
+        ["2024-01-01T00:00:00", "2024-01-01T00:01:00", "2024-01-01"],
+        dtype="datetime64[s]",
+    )
+    forecast = Forecast(lead_time=lead_times_seconds, member=[1, 2, 3])
+    npt.assert_array_equal(forecast.lead_time, lead_times_seconds, strict=True)
+    assert forecast.lead_time.dtype == np.dtype("datetime64[s]")