diff --git a/homeassistant/components/climate/__init__.py b/homeassistant/components/climate/__init__.py
index 5ae10fca303..d35b142a8c4 100644
--- a/homeassistant/components/climate/__init__.py
+++ b/homeassistant/components/climate/__init__.py
@@ -562,16 +562,15 @@ class ClimateDevice(Entity):
 
     def _convert_for_display(self, temp):
         """Convert temperature into preferred units for display purposes."""
-        if temp is None or not isinstance(temp, Number):
+        if (temp is None or not isinstance(temp, Number) or
+                self.temperature_unit == self.unit_of_measurement):
             return temp
 
         value = convert_temperature(temp, self.temperature_unit,
                                     self.unit_of_measurement)
 
-        if self.unit_of_measurement is TEMP_CELSIUS:
-            decimal_count = 1
+        if self.unit_of_measurement == TEMP_CELSIUS:
+            return round(value, 1)
         else:
             # Users of fahrenheit generally expect integer units.
-            decimal_count = 0
-
-        return round(value, decimal_count)
+            return round(value)
diff --git a/homeassistant/components/weather/__init__.py b/homeassistant/components/weather/__init__.py
index 50173840657..26a5a41bf10 100644
--- a/homeassistant/components/weather/__init__.py
+++ b/homeassistant/components/weather/__init__.py
@@ -5,7 +5,9 @@ For more details about this component, please refer to the documentation at
 https://home-assistant.io/components/weather/
 """
 import logging
+from numbers import Number
 
+from homeassistant.const import TEMP_CELSIUS
 from homeassistant.helpers.entity_component import EntityComponent
 from homeassistant.util.temperature import convert as convert_temperature
 from homeassistant.helpers.config_validation import PLATFORM_SCHEMA  # noqa
@@ -84,10 +86,7 @@ class WeatherEntity(Entity):
     def state_attributes(self):
         """Return the state attributes."""
         data = {
-            ATTR_WEATHER_TEMPERATURE:
-                convert_temperature(
-                    self.temperature, self.temperature_unit,
-                    self.hass.config.units.temperature_unit),
+            ATTR_WEATHER_TEMPERATURE: self._temp_for_display,
             ATTR_WEATHER_HUMIDITY: self.humidity,
         }
 
@@ -124,6 +123,20 @@ class WeatherEntity(Entity):
         raise NotImplementedError()
 
     @property
-    def unit_of_measurement(self):
-        """Return the unit of measurement."""
-        return None
+    def _temp_for_display(self):
+        """Convert temperature into preferred units for display purposes."""
+        temp = self.temperature
+        unit = self.temperature_unit
+        hass_unit = self.hass.config.units.temperature_unit
+
+        if (temp is None or not isinstance(temp, Number) or
+                unit == hass_unit):
+            return temp
+
+        value = convert_temperature(temp, unit, hass_unit)
+
+        if hass_unit == TEMP_CELSIUS:
+            return round(value, 1)
+        else:
+            # Users of fahrenheit generally expect integer units.
+            return round(value)
diff --git a/homeassistant/helpers/entity.py b/homeassistant/helpers/entity.py
index b707f2f7199..87b05ded264 100644
--- a/homeassistant/helpers/entity.py
+++ b/homeassistant/helpers/entity.py
@@ -259,9 +259,12 @@ class Entity(object):
         # Convert temperature if we detect one
         try:
             unit_of_measure = attr.get(ATTR_UNIT_OF_MEASUREMENT)
-            if unit_of_measure in (TEMP_CELSIUS, TEMP_FAHRENHEIT):
-                units = self.hass.config.units
-                state = str(units.temperature(float(state), unit_of_measure))
+            units = self.hass.config.units
+            if (unit_of_measure in (TEMP_CELSIUS, TEMP_FAHRENHEIT) and
+                    unit_of_measure != units.temperature_unit):
+                prec = len(state) - state.index('.') - 1 if '.' in state else 0
+                temp = units.temperature(float(state), unit_of_measure)
+                state = str(round(temp) if prec == 0 else round(temp, prec))
                 attr[ATTR_UNIT_OF_MEASUREMENT] = units.temperature_unit
         except ValueError:
             # Could not convert state to float
diff --git a/homeassistant/util/temperature.py b/homeassistant/util/temperature.py
index d6e245de04f..c773e564011 100644
--- a/homeassistant/util/temperature.py
+++ b/homeassistant/util/temperature.py
@@ -31,4 +31,4 @@ def convert(temperature: float, from_unit: str, to_unit: str) -> float:
     elif from_unit == TEMP_CELSIUS:
         return celsius_to_fahrenheit(temperature)
     else:
-        return round(fahrenheit_to_celsius(temperature), 1)
+        return fahrenheit_to_celsius(temperature)
diff --git a/tests/util/test_unit_system.py b/tests/util/test_unit_system.py
index c99c2cf87bf..83edb056139 100644
--- a/tests/util/test_unit_system.py
+++ b/tests/util/test_unit_system.py
@@ -80,7 +80,8 @@ class TestUnitSystem(unittest.TestCase):
             METRIC_SYSTEM.temperature(25, METRIC_SYSTEM.temperature_unit))
         self.assertEqual(
             26.7,
-            METRIC_SYSTEM.temperature(80, IMPERIAL_SYSTEM.temperature_unit))
+            round(METRIC_SYSTEM.temperature(
+                80, IMPERIAL_SYSTEM.temperature_unit), 1))
 
     def test_temperature_to_imperial(self):
         """Test temperature conversion to imperial system."""