Thank you kindly, Idb for a patch that solves:

llWind always returns a zero vector. In the attached 
patch the WindModule has been changed slightly to 
make wind data available for llWind

OpenSim/Region/Environment/Interfaces/IWindModule.cs

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSim Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using OpenSim.Framework;
+using OpenMetaverse;
+
+namespace OpenSim.Region.Environment.Interfaces
+{
+    public interface IWindModule : IRegionModule
+    {
+        Vector2[] WindSpeeds
+        {
+            get;
+        }
+    }
+}

OpenSim/Region/Environment/Modules/World/Wind/WindModule.cs

@@ -35,7 +35,7 @@ using OpenSim.Region.Environment.Scenes;
 
 namespace OpenSim.Region.Environment.Modules
 {
-    public class WindModule : IRegionModule
+    public class WindModule : IWindModule
     {
 
         private static readonly log4net.ILog m_log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
@@ -83,6 +83,7 @@ namespace OpenSim.Region.Environment.Modules
             scene.EventManager.OnMakeChildAgent += MakeChildAgent;
             scene.EventManager.OnAvatarEnteringNewParcel += AvatarEnteringParcel;
             scene.EventManager.OnClientClosed += ClientLoggedOut;
+            scene.RegisterModuleInterface<IWindModule>(this);
 
             GenWindPos();
 
@@ -117,6 +118,11 @@ namespace OpenSim.Region.Environment.Modules
             get { return false; }
         }
 
+        public Vector2[] WindSpeeds
+        {
+            get { return windSpeeds; }
+        }
+
         public void WindToClient(IClientAPI client)
         {
                 if (ready)

OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs

@@ -953,7 +953,21 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
         public LSL_Vector llWind(LSL_Vector offset)
         {
             m_host.AddScriptLPS(1);
-            return new LSL_Vector();
+            LSL_Vector wind = new LSL_Vector(0, 0, 0);
+            IWindModule module = World.RequestModuleInterface<IWindModule>();
+            if (module != null && module.WindSpeeds != null)
+            {
+                Vector3 pos = m_host.GetWorldPosition();
+                int x = (int)((pos.X + offset.x)/ 16);
+                int y = (int)((pos.Y + offset.y)/ 16);
+                if (x < 0) x = 0;
+                if (x > 15) x = 15;
+                if (y < 0) y = 0;
+                if (y > 15) y = 15;
+                wind.x = module.WindSpeeds[y * 16 + x].X;
+                wind.y = module.WindSpeeds[y * 16 + x].Y;
+            }
+            return wind;
         }
 
         public void llSetStatus(int status, int value)