diff --git a/homeassistant/components/sensor/wunderground.py b/homeassistant/components/sensor/wunderground.py
index 0375bb1344c..7938b17e4d6 100644
--- a/homeassistant/components/sensor/wunderground.py
+++ b/homeassistant/components/sensor/wunderground.py
@@ -14,11 +14,12 @@ import async_timeout
 import voluptuous as vol
 
 from homeassistant.helpers.typing import HomeAssistantType, ConfigType
+from homeassistant.components import sensor
 from homeassistant.components.sensor import PLATFORM_SCHEMA, ENTITY_ID_FORMAT
 from homeassistant.const import (
     CONF_MONITORED_CONDITIONS, CONF_API_KEY, CONF_LATITUDE, CONF_LONGITUDE,
     TEMP_FAHRENHEIT, TEMP_CELSIUS, LENGTH_INCHES, LENGTH_KILOMETERS,
-    LENGTH_MILES, LENGTH_FEET, ATTR_ATTRIBUTION)
+    LENGTH_MILES, LENGTH_FEET, ATTR_ATTRIBUTION, CONF_ENTITY_NAMESPACE)
 from homeassistant.exceptions import PlatformNotReady
 from homeassistant.helpers.entity import Entity, async_generate_entity_id
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
@@ -617,6 +618,8 @@ LANG_CODES = [
     'CY', 'SN', 'JI', 'YI',
 ]
 
+DEFAULT_ENTITY_NAMESPACE = 'pws'
+
 PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
     vol.Required(CONF_API_KEY): cv.string,
     vol.Optional(CONF_PWS_ID): cv.string,
@@ -627,22 +630,31 @@ PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
                   'Latitude and longitude must exist together'): cv.longitude,
     vol.Required(CONF_MONITORED_CONDITIONS):
         vol.All(cv.ensure_list, vol.Length(min=1), [vol.In(SENSOR_TYPES)]),
+    vol.Optional(CONF_ENTITY_NAMESPACE,
+                 default=DEFAULT_ENTITY_NAMESPACE): cv.string,
 })
 
+# Stores a list of entity ids we added in order to support multiple stations
+# at once.
+ADDED_ENTITY_IDS_KEY = 'wunderground_added_entity_ids'
+
 
 @asyncio.coroutine
 def async_setup_platform(hass: HomeAssistantType, config: ConfigType,
                          async_add_devices, discovery_info=None):
     """Set up the WUnderground sensor."""
+    hass.data.setdefault(ADDED_ENTITY_IDS_KEY, set())
+
     latitude = config.get(CONF_LATITUDE, hass.config.latitude)
     longitude = config.get(CONF_LONGITUDE, hass.config.longitude)
+    namespace = config.get(CONF_ENTITY_NAMESPACE)
 
     rest = WUndergroundData(
         hass, config.get(CONF_API_KEY), config.get(CONF_PWS_ID),
         config.get(CONF_LANG), latitude, longitude)
     sensors = []
     for variable in config[CONF_MONITORED_CONDITIONS]:
-        sensors.append(WUndergroundSensor(hass, rest, variable))
+        sensors.append(WUndergroundSensor(hass, rest, variable, namespace))
 
     yield from rest.async_update()
     if not rest.data:
@@ -654,7 +666,8 @@ def async_setup_platform(hass: HomeAssistantType, config: ConfigType,
 class WUndergroundSensor(Entity):
     """Implementing the WUnderground sensor."""
 
-    def __init__(self, hass: HomeAssistantType, rest, condition):
+    def __init__(self, hass: HomeAssistantType, rest, condition,
+                 namespace: str):
         """Initialize the sensor."""
         self.rest = rest
         self._condition = condition
@@ -666,8 +679,12 @@ class WUndergroundSensor(Entity):
         self._entity_picture = None
         self._unit_of_measurement = self._cfg_expand("unit_of_measurement")
         self.rest.request_feature(SENSOR_TYPES[condition].feature)
+        current_ids = set(hass.states.async_entity_ids(sensor.DOMAIN))
+        current_ids |= hass.data[ADDED_ENTITY_IDS_KEY]
         self.entity_id = async_generate_entity_id(
-            ENTITY_ID_FORMAT, "pws_" + condition, hass=hass)
+            ENTITY_ID_FORMAT, "{} {}".format(namespace, condition),
+            current_ids=current_ids)
+        hass.data[ADDED_ENTITY_IDS_KEY].add(self.entity_id)
 
     def _cfg_expand(self, what, default=None):
         """Parse and return sensor data."""
diff --git a/homeassistant/helpers/entity.py b/homeassistant/helpers/entity.py
index 4efe8d2f6c3..efaefc26184 100644
--- a/homeassistant/helpers/entity.py
+++ b/homeassistant/helpers/entity.py
@@ -4,7 +4,7 @@ import logging
 import functools as ft
 from timeit import default_timer as timer
 
-from typing import Optional, List
+from typing import Optional, List, Iterable
 
 from homeassistant.const import (
     ATTR_ASSUMED_STATE, ATTR_FRIENDLY_NAME, ATTR_HIDDEN, ATTR_ICON,
@@ -42,7 +42,7 @@ def generate_entity_id(entity_id_format: str, name: Optional[str],
 
 @callback
 def async_generate_entity_id(entity_id_format: str, name: Optional[str],
-                             current_ids: Optional[List[str]] = None,
+                             current_ids: Optional[Iterable[str]] = None,
                              hass: Optional[HomeAssistant] = None) -> str:
     """Generate a unique entity ID based on given entity IDs or used IDs."""
     if current_ids is None:
diff --git a/homeassistant/util/__init__.py b/homeassistant/util/__init__.py
index 82ba6a734f8..a8a84c6c880 100644
--- a/homeassistant/util/__init__.py
+++ b/homeassistant/util/__init__.py
@@ -13,7 +13,7 @@ from functools import wraps
 from types import MappingProxyType
 from unicodedata import normalize
 
-from typing import Any, Optional, TypeVar, Callable, Sequence, KeysView, Union
+from typing import Any, Optional, TypeVar, Callable, KeysView, Union, Iterable
 
 from .dt import as_local, utcnow
 
@@ -72,7 +72,7 @@ def convert(value: T, to_type: Callable[[T], U],
 
 
 def ensure_unique_string(preferred_string: str, current_strings:
-                         Union[Sequence[str], KeysView[str]]) -> str:
+                         Union[Iterable[str], KeysView[str]]) -> str:
     """Return a string that is not present in current_strings.
 
     If preferred string exists will append _2, _3, ..
diff --git a/tests/components/sensor/test_wunderground.py b/tests/components/sensor/test_wunderground.py
index 27047ba0ad0..65526e2d938 100644
--- a/tests/components/sensor/test_wunderground.py
+++ b/tests/components/sensor/test_wunderground.py
@@ -143,3 +143,23 @@ def test_invalid_data(hass, aioclient_mock):
     for condition in VALID_CONFIG['monitored_conditions']:
         state = hass.states.get('sensor.pws_' + condition)
         assert state.state == STATE_UNKNOWN
+
+
+async def test_entity_id_with_multiple_stations(hass, aioclient_mock):
+    """Test not generating duplicate entity ids with multiple stations."""
+    aioclient_mock.get(URL, text=load_fixture('wunderground-valid.json'))
+
+    config = [
+        VALID_CONFIG,
+        {**VALID_CONFIG, 'entity_namespace': 'hi'}
+    ]
+    await async_setup_component(hass, 'sensor', {'sensor': config})
+    await hass.async_block_till_done()
+
+    state = hass.states.get('sensor.pws_weather')
+    assert state is not None
+    assert state.state == 'Clear'
+
+    state = hass.states.get('sensor.hi_weather')
+    assert state is not None
+    assert state.state == 'Clear'