diff --git a/homeassistant/components/buienradar/sensor.py b/homeassistant/components/buienradar/sensor.py
index afce293402e..712f765237e 100644
--- a/homeassistant/components/buienradar/sensor.py
+++ b/homeassistant/components/buienradar/sensor.py
@@ -742,6 +742,7 @@ class BrSensor(SensorEntity):
     ) -> None:
         """Initialize the sensor."""
         self.entity_description = description
+        self._data: BrData | None = None
         self._measured = None
         self._attr_unique_id = (
             f"{coordinates[CONF_LATITUDE]:2.6f}{coordinates[CONF_LONGITUDE]:2.6f}"
@@ -756,17 +757,29 @@ class BrSensor(SensorEntity):
         if description.key.startswith(PRECIPITATION_FORECAST):
             self._timeframe = None
 
+    async def async_added_to_hass(self) -> None:
+        """Handle entity being added to hass."""
+        if self._data is None:
+            return
+        self._update()
+
     @callback
     def data_updated(self, data: BrData):
-        """Update data."""
-        if self._load_data(data.data) and self.hass:
+        """Handle data update."""
+        self._data = data
+        if not self.hass:
+            return
+        self._update()
+
+    def _update(self):
+        """Update sensor data."""
+        _LOGGER.debug("Updating sensor %s", self.entity_id)
+        if self._load_data(self._data.data):
             self.async_write_ha_state()
 
     @callback
     def _load_data(self, data):  # noqa: C901
         """Load the sensor with relevant data."""
-        # Find sensor
-
         # Check if we have a new measurement,
         # otherwise we do not have to update the sensor
         if self._measured == data.get(MEASURED):
diff --git a/homeassistant/components/sensor/__init__.py b/homeassistant/components/sensor/__init__.py
index 6b264efdd46..064914a5dfa 100644
--- a/homeassistant/components/sensor/__init__.py
+++ b/homeassistant/components/sensor/__init__.py
@@ -472,6 +472,11 @@ class SensorEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
         """Return translation key for unit of measurement."""
         if self.translation_key is None:
             return None
+        if self.platform is None:
+            raise ValueError(
+                f"Sensor {type(self)} cannot have a translation key for "
+                "unit of measurement before being added to the entity platform"
+            )
         platform = self.platform
         return (
             f"component.{platform.platform_name}.entity.{platform.domain}"
diff --git a/tests/components/sensor/test_init.py b/tests/components/sensor/test_init.py
index 44ad076807c..0ea46a41273 100644
--- a/tests/components/sensor/test_init.py
+++ b/tests/components/sensor/test_init.py
@@ -545,6 +545,45 @@ async def test_translated_unit_with_native_unit_raises(
         assert entity0.entity_id is None
 
 
+async def test_unit_translation_key_without_platform_raises(
+    hass: HomeAssistant,
+) -> None:
+    """Test that unit translation key property raises if the entity has no platform yet."""
+
+    with patch(
+        "homeassistant.helpers.service.translation.async_get_translations",
+        return_value={
+            "component.test.entity.sensor.test_translation_key.unit_of_measurement": "Tests"
+        },
+    ):
+        entity0 = MockSensor(
+            name="Test",
+            native_value="123",
+            unique_id="very_unique",
+        )
+        entity0.entity_description = SensorEntityDescription(
+            "test",
+            translation_key="test_translation_key",
+        )
+        with pytest.raises(
+            ValueError,
+            match="cannot have a translation key for unit of measurement before "
+            "being added to the entity platform",
+        ):
+            unit = entity0.unit_of_measurement  # noqa: F841
+
+        setup_test_component_platform(hass, sensor.DOMAIN, [entity0])
+
+        assert await async_setup_component(
+            hass, "sensor", {"sensor": {"platform": "test"}}
+        )
+        await hass.async_block_till_done()
+
+        # Should not raise after being added to the platform
+        unit = entity0.unit_of_measurement  # noqa: F841
+        assert unit == "Tests"
+
+
 @pytest.mark.parametrize(
     (
         "device_class",