diff --git a/homeassistant/components/weather/__init__.py b/homeassistant/components/weather/__init__.py
index 467a106a6a2..c36c960c4fc 100644
--- a/homeassistant/components/weather/__init__.py
+++ b/homeassistant/components/weather/__init__.py
@@ -113,9 +113,12 @@ class WeatherEntity(Entity):
             ATTR_WEATHER_TEMPERATURE: show_temp(
                 self.hass, self.temperature, self.temperature_unit,
                 self.precision),
-            ATTR_WEATHER_HUMIDITY: round(self.humidity)
         }
 
+        humidity = self.humidity
+        if humidity is not None:
+            data[ATTR_WEATHER_HUMIDITY] = round(humidity)
+
         ozone = self.ozone
         if ozone is not None:
             data[ATTR_WEATHER_OZONE] = ozone