diff --git a/src/mudlib/commands/look.py b/src/mudlib/commands/look.py
index 76b0592..7051d56 100644
--- a/src/mudlib/commands/look.py
+++ b/src/mudlib/commands/look.py
@@ -4,16 +4,24 @@ from mudlib.commands import CommandDefinition, register
 from mudlib.commands.things import _format_thing_name
 from mudlib.effects import get_effects_at
 from mudlib.entity import Entity
+from mudlib.gametime import get_game_day, get_game_hour
 from mudlib.player import Player
 from mudlib.render.ansi import RESET, colorize_terrain
 from mudlib.render.room import (
+    render_atmosphere,
     render_entity_lines,
     render_exits,
     render_location,
     render_nearby,
     render_where,
 )
+from mudlib.seasons import get_season
 from mudlib.thing import Thing
+from mudlib.weather import (
+    WeatherCondition,
+    get_current_weather,
+    get_weather_description,
+)
 from mudlib.zone import Zone
 
 # Viewport dimensions
@@ -160,6 +168,25 @@ async def cmd_look(player: Player, args: str) -> None:
     # Where header
     output.append(render_where(zone.description))
 
+    # Atmosphere line (between Where and viewport)
+    try:
+        hour = get_game_hour()
+        day = get_game_day()
+        weather = get_current_weather()
+        season = get_season(day)
+
+        # Get weather description (empty string for clear)
+        if weather.condition == WeatherCondition.clear:
+            weather_desc = ""
+        else:
+            weather_desc = get_weather_description(weather)
+
+        atmosphere = render_atmosphere(hour, weather_desc, season)
+        output.append(atmosphere)
+    except RuntimeError:
+        # Game time not initialized, skip atmosphere
+        pass
+
     # Viewport
     output.append("\r\n".join(output_lines))
 
diff --git a/src/mudlib/render/room.py b/src/mudlib/render/room.py
index 43b51fe..443be91 100644
--- a/src/mudlib/render/room.py
+++ b/src/mudlib/render/room.py
@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+from mudlib.timeofday import get_sky_description, get_time_period
+
 
 def render_where(zone_name: str) -> str:
     """Render the zone description line.
@@ -137,3 +139,23 @@ def render_entity_lines(entities: list, viewer) -> str:
         lines.append(f"{entity.name} {msg}")
 
     return "\n".join(lines)
+
+
+def render_atmosphere(hour: int, weather_desc: str, season: str) -> str:
+    """Render atmosphere line combining time-of-day and weather.
+
+    Args:
+        hour: Game hour (0-23)
+        weather_desc: Weather description (empty string for clear weather)
+        season: Season name ("spring", "summer", "autumn", "winter")
+
+    Returns:
+        Formatted atmosphere line
+    """
+    sky = get_sky_description(hour)
+    period = get_time_period(hour)
+
+    if weather_desc:
+        return f"{sky}. {weather_desc}. [{period}, {season}]"
+    else:
+        return f"{sky}. [{period}, {season}]"
diff --git a/src/mudlib/weather.py b/src/mudlib/weather.py
index 7771639..4002301 100644
--- a/src/mudlib/weather.py
+++ b/src/mudlib/weather.py
@@ -221,3 +221,43 @@ def advance_weather(
         new_intensity = rng.uniform(0.0, 1.0)
 
     return WeatherState(condition=new_condition, intensity=new_intensity)
+
+
+# Global weather state
+_current_weather: WeatherState | None = None
+
+
+def init_weather(
+    condition: WeatherCondition = WeatherCondition.clear, intensity: float = 0.5
+) -> None:
+    """Initialize the global weather state.
+
+    Args:
+        condition: Initial weather condition
+        intensity: Initial intensity (0.0 to 1.0)
+    """
+    global _current_weather
+    _current_weather = WeatherState(condition=condition, intensity=intensity)
+
+
+def get_current_weather() -> WeatherState:
+    """Get the current global weather state.
+
+    Returns:
+        Current weather state (defaults to clear if not initialized)
+    """
+    if _current_weather is None:
+        return WeatherState(condition=WeatherCondition.clear, intensity=0.5)
+    return _current_weather
+
+
+def tick_weather(season: str = "summer", climate: str = "temperate") -> None:
+    """Advance weather by one step. Called once per game hour.
+
+    Args:
+        season: Current season
+        climate: Climate profile to use
+    """
+    global _current_weather
+    current = get_current_weather()
+    _current_weather = advance_weather(current, season=season, climate=climate)
diff --git a/tests/test_gametime.py b/tests/test_gametime.py
index 916c01b..681e866 100644
--- a/tests/test_gametime.py
+++ b/tests/test_gametime.py
@@ -7,6 +7,14 @@ import pytest
 from mudlib.gametime import GameTime, get_game_day, get_game_hour, init_game_time
 
 
+@pytest.fixture(autouse=True)
+def _reset_globals():
+    yield
+    import mudlib.gametime
+
+    mudlib.gametime._game_time = None
+
+
 def test_get_game_hour_at_epoch():
     """Game hour should be 0 at epoch."""
     epoch = time.time()
diff --git a/tests/test_look_command.py b/tests/test_look_command.py
index f87ad2b..4e4bbf0 100644
--- a/tests/test_look_command.py
+++ b/tests/test_look_command.py
@@ -1,5 +1,6 @@
 """Tests for the look command with structured room display."""
 
+import time
 from unittest.mock import AsyncMock, MagicMock
 
 import pytest
@@ -7,12 +8,24 @@ import pytest
 from mudlib.commands import look  # noqa: F401
 from mudlib.commands.look import cmd_look
 from mudlib.entity import Mob
+from mudlib.gametime import init_game_time
 from mudlib.player import Player
 from mudlib.portal import Portal
 from mudlib.thing import Thing
+from mudlib.weather import WeatherCondition, init_weather
 from mudlib.zone import Zone
 
 
+@pytest.fixture(autouse=True)
+def _reset_globals():
+    yield
+    import mudlib.gametime
+    import mudlib.weather
+
+    mudlib.gametime._game_time = None
+    mudlib.weather._current_weather = None
+
+
 @pytest.fixture
 def mock_writer():
     writer = MagicMock()
@@ -203,3 +216,124 @@ async def test_look_nowhere(mock_reader, mock_writer):
     output = get_output(player)
 
     assert "You are nowhere." in output
+
+
+@pytest.mark.asyncio
+async def test_look_includes_atmosphere_clear():
+    """Look should include atmosphere line with clear weather."""
+    # Initialize game time and weather
+    init_game_time(epoch=time.time(), real_minutes_per_game_hour=1.0)
+    init_weather(condition=WeatherCondition.clear, intensity=0.5)
+
+    # Create player
+    mock_reader = MagicMock()
+    mock_writer = MagicMock()
+    mock_writer.write = MagicMock()
+    mock_writer.drain = AsyncMock()
+
+    terrain = [["." for _ in range(50)] for _ in range(50)]
+    zone = Zone(
+        name="test_zone",
+        description="The Test Zone",
+        width=50,
+        height=50,
+        terrain=terrain,
+        impassable={"^", "~"},
+    )
+
+    player = Player(
+        name="TestPlayer", x=25, y=25, reader=mock_reader, writer=mock_writer
+    )
+    player.location = zone
+    zone._contents.append(player)
+
+    await cmd_look(player, "")
+    output = get_output(player)
+
+    # Should see atmosphere line with period and season
+    assert "[" in output and "]" in output
+    # Should not have weather description for clear weather
+    # (the format is: sky. [period, season])
+    seasons = ["spring]", "summer]", "autumn]", "winter]"]
+    assert any(season in output for season in seasons)
+
+
+@pytest.mark.asyncio
+async def test_look_includes_atmosphere_with_rain():
+    """Look should include atmosphere line with rain."""
+    # Initialize game time and weather
+    init_game_time(epoch=time.time(), real_minutes_per_game_hour=1.0)
+    init_weather(condition=WeatherCondition.rain, intensity=0.5)
+
+    # Create player
+    mock_reader = MagicMock()
+    mock_writer = MagicMock()
+    mock_writer.write = MagicMock()
+    mock_writer.drain = AsyncMock()
+
+    terrain = [["." for _ in range(50)] for _ in range(50)]
+    zone = Zone(
+        name="test_zone",
+        description="The Test Zone",
+        width=50,
+        height=50,
+        terrain=terrain,
+        impassable={"^", "~"},
+    )
+
+    player = Player(
+        name="TestPlayer", x=25, y=25, reader=mock_reader, writer=mock_writer
+    )
+    player.location = zone
+    zone._contents.append(player)
+
+    await cmd_look(player, "")
+    output = get_output(player)
+
+    # Should see atmosphere line with rain description
+    assert "rain" in output.lower()
+    # Should see season tag
+    assert "[" in output and "]" in output
+
+
+@pytest.mark.asyncio
+async def test_look_atmosphere_between_where_and_viewport():
+    """Atmosphere line should appear between Where header and viewport."""
+    # Initialize game time and weather
+    init_game_time(epoch=time.time(), real_minutes_per_game_hour=1.0)
+    init_weather(condition=WeatherCondition.clear, intensity=0.5)
+
+    # Create player
+    mock_reader = MagicMock()
+    mock_writer = MagicMock()
+    mock_writer.write = MagicMock()
+    mock_writer.drain = AsyncMock()
+
+    terrain = [["." for _ in range(50)] for _ in range(50)]
+    zone = Zone(
+        name="test_zone",
+        description="The Test Zone",
+        width=50,
+        height=50,
+        terrain=terrain,
+        impassable={"^", "~"},
+    )
+
+    player = Player(
+        name="TestPlayer", x=25, y=25, reader=mock_reader, writer=mock_writer
+    )
+    player.location = zone
+    zone._contents.append(player)
+
+    await cmd_look(player, "")
+    output = get_output(player)
+
+    # Find positions of key sections
+    where_pos = output.find("Where:")
+    location_pos = output.find("Location:")
+
+    # Atmosphere should be between Where and Location
+    # Look for a bracket tag (season indicator)
+    bracket_pos = output.find("[")
+
+    assert where_pos < bracket_pos < location_pos
diff --git a/tests/test_npc_schedule.py b/tests/test_npc_schedule.py
index 671ae9f..771b125 100644
--- a/tests/test_npc_schedule.py
+++ b/tests/test_npc_schedule.py
@@ -26,6 +26,14 @@ def clear_mobs():
     mob_templates.clear()
 
 
+@pytest.fixture(autouse=True)
+def _reset_globals():
+    yield
+    import mudlib.gametime
+
+    mudlib.gametime._game_time = None
+
+
 def test_schedule_entry_creation():
     """ScheduleEntry can be created with required fields."""
     entry = ScheduleEntry(hour=6, state="working")
diff --git a/tests/test_render_room.py b/tests/test_render_room.py
new file mode 100644
index 0000000..2bb5d02
--- /dev/null
+++ b/tests/test_render_room.py
@@ -0,0 +1,145 @@
+"""Tests for room rendering functions."""
+
+from mudlib.render.room import (
+    render_atmosphere,
+    render_entity_lines,
+    render_exits,
+    render_location,
+    render_nearby,
+    render_where,
+)
+
+
+class MockZone:
+    """Mock zone for testing."""
+
+    def __init__(self, width=100, height=100, passable_tiles=None):
+        self.width = width
+        self.height = height
+        self.description = "Test Zone"
+        self._passable = passable_tiles or set()
+
+    def is_passable(self, x, y):
+        return (x, y) in self._passable
+
+
+class MockEntity:
+    """Mock entity for testing."""
+
+    def __init__(self, name, posture="standing"):
+        self.name = name
+        self.posture = posture
+
+
+def test_render_where():
+    """render_where should format zone description."""
+    assert render_where("The Overworld") == "Where: The Overworld"
+
+
+def test_render_location_center():
+    """render_location should show center quadrant."""
+    zone = MockZone(width=90, height=90)
+    assert render_location(zone, 45, 45) == "Location: center 45, 45"
+
+
+def test_render_location_northeast():
+    """render_location should show northeast quadrant."""
+    zone = MockZone(width=90, height=90)
+    assert render_location(zone, 70, 10) == "Location: northeast 70, 10"
+
+
+def test_render_location_southwest():
+    """render_location should show southwest quadrant."""
+    zone = MockZone(width=90, height=90)
+    assert render_location(zone, 10, 70) == "Location: southwest 10, 70"
+
+
+def test_render_nearby_empty():
+    """render_nearby should return empty string when no entities."""
+    assert render_nearby([], None) == ""
+
+
+def test_render_nearby_with_entities():
+    """render_nearby should show count and names."""
+    entities = [MockEntity("Goku"), MockEntity("Vegeta")]
+    result = render_nearby(entities, None)
+    assert result == "Nearby: (2) Goku / Vegeta"
+
+
+def test_render_exits_all_directions():
+    """render_exits should list all passable directions."""
+    zone = MockZone(passable_tiles={(5, 4), (5, 6), (6, 5), (4, 5)})
+    assert render_exits(zone, 5, 5) == "Exits: north south east west"
+
+
+def test_render_exits_partial():
+    """render_exits should list only passable directions."""
+    zone = MockZone(passable_tiles={(5, 4), (6, 5)})
+    assert render_exits(zone, 5, 5) == "Exits: north east"
+
+
+def test_render_exits_none():
+    """render_exits should show 'Exits:' with no directions if trapped."""
+    zone = MockZone(passable_tiles=set())
+    assert render_exits(zone, 5, 5) == "Exits:"
+
+
+def test_render_entity_lines_empty():
+    """render_entity_lines should return empty string when no entities."""
+    assert render_entity_lines([], None) == ""
+
+
+def test_render_entity_lines_with_postures():
+    """render_entity_lines should show entity names with postures."""
+    entities = [
+        MockEntity("Krillin", "resting"),
+        MockEntity("Piccolo", "standing"),
+    ]
+    result = render_entity_lines(entities, None)
+    assert "Krillin is resting here." in result
+    assert "Piccolo is standing here." in result
+
+
+def test_render_atmosphere_clear_weather():
+    """render_atmosphere should omit weather desc when clear."""
+    result = render_atmosphere(12, "", "summer")
+    assert "[day, summer]" in result
+    # Should have sky description but no weather text
+    assert result.count(". [") == 1  # only one period before bracket
+    # Should not have double period before bracket
+    assert ". . [" not in result
+
+
+def test_render_atmosphere_with_rain():
+    """render_atmosphere should include weather desc when not clear."""
+    result = render_atmosphere(12, "rain patters steadily", "spring")
+    assert "rain patters steadily" in result
+    assert "[day, spring]" in result
+
+
+def test_render_atmosphere_dawn():
+    """render_atmosphere should show dawn period."""
+    result = render_atmosphere(5, "", "autumn")
+    assert "[dawn, autumn]" in result
+
+
+def test_render_atmosphere_dusk():
+    """render_atmosphere should show dusk period."""
+    result = render_atmosphere(18, "", "winter")
+    assert "[dusk, winter]" in result
+
+
+def test_render_atmosphere_night():
+    """render_atmosphere should show night period."""
+    result = render_atmosphere(22, "", "spring")
+    assert "[night, spring]" in result
+
+
+def test_render_atmosphere_with_heavy_snow():
+    """render_atmosphere should include heavy weather descriptions."""
+    result = render_atmosphere(22, "heavy snow blankets everything", "winter")
+    assert "heavy snow blankets everything" in result
+    assert "[night, winter]" in result
+    # Should have format: sky. weather. [period, season]
+    parts = result.split(". ")
+    assert len(parts) == 3  # sky, weather, [period, season]