diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
index 5f8d8f1ab8..90f0336869 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs
@@ -1390,11 +1390,12 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         ///  Send the cloud matrix to the client
         /// </summary>
         /// <param name="windSpeeds">16x16 array of cloud densities</param>
+/*
         public virtual void SendCloudData(int version, float[] cloudDensity)
         {
             Util.FireAndForget(DoSendCloudData, cloudDensity, "LLClientView.SendCloudData");
         }
-
+*/
         // wind caching
         private static int lastWindVersion = 0;
         private static List<LayerDataPacket> lastWindPackets = new List<LayerDataPacket>();
@@ -1445,30 +1446,53 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     OutPacket(pkt, ThrottleOutPacketType.Wind);
         }
 
+        // cloud caching
+        private static int lastCloudVersion = 0;
+        private static List<LayerDataPacket> lastCloudPackets = new List<LayerDataPacket>();
+
         /// <summary>
         /// Send cloud layer information to the client.
         /// </summary>
         /// <param name="o"></param>
-        private void DoSendCloudData(object o)
+//        private void DoSendCloudData(object o)
+        public virtual void SendCloudData(int version, float[] cloudDensity)
         {
-            float[] cloudCover = (float[])o;
-            TerrainPatch[] patches = new TerrainPatch[1];
-            patches[0] = new TerrainPatch();
-            patches[0].Data = new float[16 * 16];
+//            float[] cloudDensity = (float[])o;
+            bool isNewData;
+            lock(lastCloudPackets)
+                isNewData = lastCloudVersion != version;
 
-            for (int y = 0; y < 16; y++)
+            if(isNewData)
             {
-                for (int x = 0; x < 16; x++)
+                TerrainPatch[] patches = new TerrainPatch[1];
+                patches[0] = new TerrainPatch();
+                patches[0].Data = new float[16 * 16];
+
+                for (int y = 0; y < 16; y++)
                 {
-                    patches[0].Data[y * 16 + x] = cloudCover[y * 16 + x];
+                    for (int x = 0; x < 16; x++)
+                    {
+                        patches[0].Data[y * 16 + x] = cloudDensity[y * 16 + x];
+                    }
+                }
+                // neither we or viewers have extended clouds
+                byte layerType = (byte)TerrainPatch.LayerType.Cloud;
+
+                LayerDataPacket layerpack =
+                    OpenSimTerrainCompressor.CreateLayerDataPacketStandardSize(
+                        patches, layerType);
+                layerpack.Header.Zerocoded = true;
+                lock(lastCloudPackets)
+                {
+                    lastCloudPackets.Clear();
+                    lastCloudPackets.Add(layerpack);
+                    lastCloudVersion = version;
                 }
             }
-            // neither we or viewers have extended clouds
-            byte layerType = (byte)TerrainPatch.LayerType.Cloud;
 
-            LayerDataPacket layerpack = OpenSimTerrainCompressor.CreateLayerDataPacketStandardSize(patches, layerType);
-            layerpack.Header.Zerocoded = true;
-            OutPacket(layerpack, ThrottleOutPacketType.Cloud);
+            lock(lastCloudPackets)
+                foreach(LayerDataPacket pkt in lastCloudPackets)
+                    OutPacket(pkt, ThrottleOutPacketType.Cloud);
         }
 
         /// <summary>
diff --git a/OpenSim/Region/CoreModules/World/Cloud/CloudModule.cs b/OpenSim/Region/CoreModules/World/Cloud/CloudModule.cs
index f304307586..3c2884b385 100644
--- a/OpenSim/Region/CoreModules/World/Cloud/CloudModule.cs
+++ b/OpenSim/Region/CoreModules/World/Cloud/CloudModule.cs
@@ -27,6 +27,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Threading;
 using Mono.Addins;
 using Nini.Config;
 using OpenMetaverse;
@@ -49,6 +50,10 @@ namespace OpenSim.Region.CoreModules.World
         private bool m_enabled = false;
         private float m_cloudDensity = 1.0F;
         private float[] cloudCover = new float[16 * 16];
+        private int m_dataVersion;
+        private bool m_busy;
+        private object cloudlock = new object();
+
 
         public void Initialise(IConfigSource config)
         {
@@ -70,11 +75,13 @@ namespace OpenSim.Region.CoreModules.World
 
             m_scene = scene;
 
-            scene.EventManager.OnNewClient += CloudsToClient;
             scene.RegisterModuleInterface<ICloudModule>(this);
-            scene.EventManager.OnFrame += CloudUpdate;
 
             GenerateCloudCover();
+            m_dataVersion = (int)m_scene.AllocateLocalId();
+
+            scene.EventManager.OnNewClient += CloudsToClient;
+            scene.EventManager.OnFrame += CloudUpdate;
 
             m_ready = true;
         }
@@ -89,7 +96,6 @@ namespace OpenSim.Region.CoreModules.World
             m_scene.EventManager.OnNewClient -= CloudsToClient;
             m_scene.EventManager.OnFrame -= CloudUpdate;
             m_scene.UnregisterModuleInterface<ICloudModule>(this);
-
             m_scene = null;
         }
 
@@ -127,7 +133,8 @@ namespace OpenSim.Region.CoreModules.World
 
             if (cloudCover != null)
             {
-                cover = cloudCover[y * 16 + x];
+                lock(cloudlock)
+                    cover = cloudCover[y * 16 + x];
             }
 
             return cover;
@@ -188,22 +195,48 @@ namespace OpenSim.Region.CoreModules.World
                 }
             }
             Array.Copy(newCover, cloudCover, 16 * 16);
+            m_dataVersion++;
         }
   
-       private void CloudUpdate()
-       {
-           if (((m_frame++ % m_frameUpdateRate) != 0) || !m_ready || (m_cloudDensity == 0))
-           {
-               return;
-           }
-           UpdateCloudCover();
+        private void CloudUpdate()
+        {
+            if ((!m_ready || m_cloudDensity == 0 || (m_frame++ % m_frameUpdateRate) != 0))
+            {
+                return;
+            }
+
+            if(Monitor.TryEnter(cloudlock))
+            {
+                m_busy = true;
+                Util.FireAndForget(delegate
+                    {
+                        try
+                        {
+                            lock(cloudlock)
+                            {
+                                UpdateCloudCover();
+                                m_scene.ForEachClient(delegate(IClientAPI client)
+                                {
+                                    client.SendCloudData(m_dataVersion, cloudCover);
+                                });
+                            }
+                        }
+                        finally
+                        {
+                            m_busy = false;
+                        }
+                    },
+                    null, "CloudModuleUpdate");
+                Monitor.Exit(cloudlock);
+            }
         }
 
         public void CloudsToClient(IClientAPI client)
         {
             if (m_ready)
             {
-                client.SendCloudData(0, cloudCover);
+                lock(cloudlock)
+                       client.SendCloudData(m_dataVersion, cloudCover);
             }
         }
 
diff --git a/OpenSim/Region/CoreModules/World/Wind/WindModule.cs b/OpenSim/Region/CoreModules/World/Wind/WindModule.cs
index bc92582c30..95cf57d20d 100644
--- a/OpenSim/Region/CoreModules/World/Wind/WindModule.cs
+++ b/OpenSim/Region/CoreModules/World/Wind/WindModule.cs
@@ -425,7 +425,7 @@ namespace OpenSim.Region.CoreModules
                 try
                 {
                     GenWind();
-                    m_scene.ForEachRootClient(delegate(IClientAPI client)
+                    m_scene.ForEachClient(delegate(IClientAPI client)
                     {
                         client.SendWindData(m_dataVersion, windSpeeds);
                     });