diff --git a/src/itzi/providers/grass_interface.py b/src/itzi/providers/grass_interface.py
index d145db62..eef5466d 100644
--- a/src/itzi/providers/grass_interface.py
+++ b/src/itzi/providers/grass_interface.py
@@ -369,6 +369,14 @@ def get_sim_extend_in_stds_unit(self, strds) -> tuple[int | datetime, int | date
             # get start time and end time in seconds
             rel_end_time = (self.end_time - self.start_time).total_seconds()
             rel_unit = strds.get_relative_time_unit()
+            if rel_unit not in self.t_unit_conv:
+                supported_units = ", ".join(sorted(self.t_unit_conv))
+                if rel_unit is None:
+                    msgr.fatal(f"STRDS <{strds.get_id()}> has no relative time unit")
+                msgr.fatal(
+                    f"STRDS <{strds.get_id()}> uses unsupported relative time unit "
+                    f"<{rel_unit}>; supported units are {supported_units}"
+                )
             start_time_in_stds_unit = 0
             end_time_in_stds_unit = self.from_s(rel_unit, rel_end_time)
         elif strds.get_temporal_type() == TemporalType.ABSOLUTE:
@@ -387,6 +395,12 @@ def stds_temporal_sanity(self, stds_id: str) -> bool:
         """
         out = True
         stds = tgis.open_stds.open_old_stds(stds_id, "strds")
+        stds_start, stds_end = stds.get_temporal_extent_as_tuple()
+        if stds_start is None or stds_end is None:
+            msgr.fatal(
+                f"STRDS <{stds_id}> has no temporal extent; "
+                "make sure it contains registered raster maps"
+            )
         # valid topology
         if not stds.check_temporal_topology():
             out = False
@@ -397,7 +411,6 @@ def stds_temporal_sanity(self, stds_id: str) -> bool:
             msgr.warning("{}: gaps found".format(stds_id))
         # cover all simulation time
         sim_start, sim_end = self.get_sim_extend_in_stds_unit(stds)
-        stds_start, stds_end = stds.get_temporal_extent_as_tuple()
         if stds_start > sim_start:
             out = False
             msgr.warning("{}: starts after simulation".format(stds_id))
diff --git a/tests/grass/test_itzi.py b/tests/grass/test_itzi.py
index d10b3159..bcdec638 100644
--- a/tests/grass/test_itzi.py
+++ b/tests/grass/test_itzi.py
@@ -195,6 +195,87 @@ def test_fails_when_region_has_no_dem_data(test_data_temp_path):
         SimulationRunner(conf_data.get_sim_params(), conf_data.get_grass_params())
 
 
+@pytest.mark.forked
+@pytest.mark.usefixtures("grass_5by5")
+@pytest.mark.parametrize("temporal_type", ["relative", "absolute"])
+def test_empty_strds_fails_with_clear_error(test_data_temp_path, temporal_type: str):
+    current_mapset = gscript.read_command("g.mapset", flags="p").rstrip()
+    strds_name = f"empty_{temporal_type}_rain_{uuid4().hex[:8]}"
+    gscript.run_command(
+        "t.create",
+        output=strds_name,
+        type="strds",
+        temporaltype=temporal_type,
+        semantictype="mean",
+        title=strds_name,
+        description=strds_name,
+    )
+
+    input_names = {
+        "rain": f"{strds_name}@{current_mapset}",
+        "water_depth": f"start_h@{current_mapset}",
+    }
+    with pytest.raises(
+        RuntimeError,
+        match=rf"STRDS <{strds_name}@{current_mapset}> has no temporal extent",
+    ):
+        _build_timed_rain_runner(
+            test_data_temp_path,
+            input_names=input_names,
+            duration="00:00:20",
+            record_step="00:00:20",
+            prefix=f"out_empty_{temporal_type}_{uuid4().hex[:8]}",
+        )
+
+
+@pytest.mark.forked
+@pytest.mark.usefixtures("grass_5by5")
+def test_relative_strds_with_unsupported_unit_fails_with_clear_error(test_data_temp_path):
+    current_mapset = gscript.read_command("g.mapset", flags="p").rstrip()
+    suffix = uuid4().hex[:8]
+    strds_name = f"monthly_rain_{suffix}"
+    rain_map_name = f"monthly_rain_map_{suffix}"
+    gscript.mapcalc(f"{rain_map_name}=10")
+    gscript.run_command(
+        "t.create",
+        output=strds_name,
+        type="strds",
+        temporaltype="relative",
+        semantictype="mean",
+        title=strds_name,
+        description=strds_name,
+    )
+    gscript.run_command(
+        "t.register",
+        flags="i",
+        input=strds_name,
+        type="raster",
+        maps=rain_map_name,
+        start="0",
+        increment="1",
+        unit="months",
+    )
+
+    input_names = {
+        "rain": f"{strds_name}@{current_mapset}",
+        "water_depth": f"start_h@{current_mapset}",
+    }
+    with pytest.raises(
+        RuntimeError,
+        match=(
+            rf"STRDS <{strds_name}@{current_mapset}> uses unsupported relative time unit "
+            r"<months>"
+        ),
+    ):
+        _build_timed_rain_runner(
+            test_data_temp_path,
+            input_names=input_names,
+            duration="00:00:20",
+            record_step="00:00:20",
+            prefix=f"out_monthly_relative_{uuid4().hex[:8]}",
+        )
+
+
 @pytest.mark.forked
 @pytest.mark.usefixtures("grass_5by5")
 @pytest.mark.parametrize(