diff --git a/homeassistant/components/metoffice/const.py b/homeassistant/components/metoffice/const.py
index e413b102898..d1f48eb4f2c 100644
--- a/homeassistant/components/metoffice/const.py
+++ b/homeassistant/components/metoffice/const.py
@@ -24,6 +24,8 @@ DOMAIN = "metoffice"
 DEFAULT_NAME = "Met Office"
 ATTRIBUTION = "Data provided by the Met Office"
 
+ATTR_FORECAST_DAYTIME = "daytime"
+
 DEFAULT_SCAN_INTERVAL = timedelta(minutes=15)
 
 METOFFICE_COORDINATES = "metoffice_coordinates"
diff --git a/homeassistant/components/metoffice/weather.py b/homeassistant/components/metoffice/weather.py
index 79363db3667..d25df1d2654 100644
--- a/homeassistant/components/metoffice/weather.py
+++ b/homeassistant/components/metoffice/weather.py
@@ -15,6 +15,7 @@ from homeassistant.helpers.update_coordinator import CoordinatorEntity
 
 from . import get_device_info
 from .const import (
+    ATTR_FORECAST_DAYTIME,
     ATTRIBUTION,
     CONDITION_CLASSES,
     DEFAULT_NAME,
@@ -46,7 +47,7 @@ async def async_setup_entry(
     )
 
 
-def _build_forecast_data(timestep):
+def _build_forecast_data(timestep, use_3hourly):
     data = {}
     data[ATTR_FORECAST_TIME] = timestep.date.isoformat()
     if timestep.weather:
@@ -59,6 +60,9 @@ def _build_forecast_data(timestep):
         data[ATTR_FORECAST_WIND_BEARING] = timestep.wind_direction.value
     if timestep.wind_speed:
         data[ATTR_FORECAST_WIND_SPEED] = timestep.wind_speed.value
+    if not use_3hourly:
+        # if it's close to noon, mark as Day, otherwise as Night
+        data[ATTR_FORECAST_DAYTIME] = abs(timestep.date.hour - 12) < 6
     return data
 
 
@@ -82,6 +86,7 @@ class MetOfficeWeather(CoordinatorEntity, WeatherEntity):
         )
         self._attr_name = f"{DEFAULT_NAME} {hass_data[METOFFICE_NAME]} {mode_label}"
         self._attr_unique_id = hass_data[METOFFICE_COORDINATES]
+        self._use_3hourly = use_3hourly
         if not use_3hourly:
             self._attr_unique_id = f"{self._attr_unique_id}_{MODE_DAILY}"
 
@@ -155,7 +160,7 @@ class MetOfficeWeather(CoordinatorEntity, WeatherEntity):
         if self.coordinator.data.forecast is None:
             return None
         return [
-            _build_forecast_data(timestep)
+            _build_forecast_data(timestep, self._use_3hourly)
             for timestep in self.coordinator.data.forecast
         ]
 
diff --git a/tests/components/metoffice/test_weather.py b/tests/components/metoffice/test_weather.py
index 158e44ca15b..1970217db5b 100644
--- a/tests/components/metoffice/test_weather.py
+++ b/tests/components/metoffice/test_weather.py
@@ -181,6 +181,13 @@ async def test_one_weather_site_running(hass, requests_mock, legacy_patchable_ti
     assert weather.attributes.get("forecast")[7]["temperature"] == 13
     assert weather.attributes.get("forecast")[7]["wind_speed"] == 13
     assert weather.attributes.get("forecast")[7]["wind_bearing"] == "SE"
+    assert weather.attributes.get("forecast")[7]["daytime"] is True
+
+    # Check that night entry is correctly marked as Night
+    assert (
+        weather.attributes.get("forecast")[6]["datetime"] == "2020-04-29T00:00:00+00:00"
+    )
+    assert weather.attributes.get("forecast")[6]["daytime"] is False
 
 
 @patch(
@@ -256,6 +263,7 @@ async def test_two_weather_sites_running(hass, requests_mock, legacy_patchable_t
     assert weather.attributes.get("forecast")[18]["temperature"] == 9
     assert weather.attributes.get("forecast")[18]["wind_speed"] == 4
     assert weather.attributes.get("forecast")[18]["wind_bearing"] == "NW"
+    assert "daytime" not in weather.attributes.get("forecast")[18]
 
     # Wavertree daily weather platform expected results
     weather = hass.states.get("weather.met_office_wavertree_daily")
@@ -279,6 +287,7 @@ async def test_two_weather_sites_running(hass, requests_mock, legacy_patchable_t
     assert weather.attributes.get("forecast")[7]["temperature"] == 13
     assert weather.attributes.get("forecast")[7]["wind_speed"] == 13
     assert weather.attributes.get("forecast")[7]["wind_bearing"] == "SE"
+    assert weather.attributes.get("forecast")[7]["daytime"] is True
 
     # King's Lynn 3-hourly weather platform expected results
     weather = hass.states.get("weather.met_office_king_s_lynn_3_hourly")
@@ -303,6 +312,7 @@ async def test_two_weather_sites_running(hass, requests_mock, legacy_patchable_t
     assert weather.attributes.get("forecast")[18]["temperature"] == 10
     assert weather.attributes.get("forecast")[18]["wind_speed"] == 7
     assert weather.attributes.get("forecast")[18]["wind_bearing"] == "SE"
+    assert "daytime" not in weather.attributes.get("forecast")[18]
 
     # King's Lynn daily weather platform expected results
     weather = hass.states.get("weather.met_office_king_s_lynn_daily")
@@ -326,3 +336,4 @@ async def test_two_weather_sites_running(hass, requests_mock, legacy_patchable_t
     assert weather.attributes.get("forecast")[5]["temperature"] == 11
     assert weather.attributes.get("forecast")[5]["wind_speed"] == 7
     assert weather.attributes.get("forecast")[5]["wind_bearing"] == "ESE"
+    assert weather.attributes.get("forecast")[5]["daytime"] is True