diff --git a/apps/openmw/mwworld/weather.cpp b/apps/openmw/mwworld/weather.cpp
index 14d88a752..719aef837 100644
--- a/apps/openmw/mwworld/weather.cpp
+++ b/apps/openmw/mwworld/weather.cpp
@@ -748,7 +748,7 @@ void WeatherManager::update(float duration, bool paused, const TimeStamp& time,
         }
         else
         {
-            theta = static_cast<float>(osg::PI) + static_cast<float>(osg::PI) * (adjustedHour - adjustedNightStart) / nightDuration;
+            theta = static_cast<float>(osg::PI) - static_cast<float>(osg::PI) * (adjustedHour - adjustedNightStart) / nightDuration;
         }
 
         osg::Vec3f final(