diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 2c3efe11f09..b85ddf0bada 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -83,6 +83,9 @@ Bug Fixes
   contents to ensure we don't expose pending deletes if both directory point to the same
   underlying filesystem directory. (Simon Willnauer)
 
+* LUCENE-8853: FileSwitchDirectory now applies best effort to place tmp files in the same
+  direcotry as the target files. (Simon Willnauer)
+
 Improvements
 
 * LUCENE-7840: Non-scoring BooleanQuery now removes SHOULD clauses before building the scorer supplier
diff --git a/lucene/core/src/java/org/apache/lucene/store/Directory.java b/lucene/core/src/java/org/apache/lucene/store/Directory.java
index 13e8e904b2e..5763d2c4eac 100644
--- a/lucene/core/src/java/org/apache/lucene/store/Directory.java
+++ b/lucene/core/src/java/org/apache/lucene/store/Directory.java
@@ -24,6 +24,7 @@ import java.nio.file.NoSuchFileException;
 import java.util.Collection; // for javadocs
 import java.util.Set;
 
+import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.util.IOUtils;
 
 /**
@@ -207,4 +208,13 @@ public abstract class Directory implements Closeable {
    * @lucene.internal
    */
   public abstract Set<String> getPendingDeletions() throws IOException;
+
+  /**
+   * Creates a file name for a temporary file. The name will start with
+   * {@code prefix}, end with {@code suffix} and have a reserved file extension {@code .tmp}.
+   * @see #createTempOutput(String, String, IOContext)
+   */
+  protected static String getTempFileName(String prefix, String suffix, long counter) {
+    return IndexFileNames.segmentFileName(prefix, suffix + "_" + Long.toString(counter, Character.MAX_RADIX), "tmp");
+  }
 }
diff --git a/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java b/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
index 615c089edea..cbaafb2f86d 100644
--- a/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
+++ b/lucene/core/src/java/org/apache/lucene/store/FSDirectory.java
@@ -41,7 +41,6 @@ import java.util.concurrent.Future;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
-import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.util.Constants;
 import org.apache.lucene.util.IOUtils;
 
@@ -261,7 +260,7 @@ public abstract class FSDirectory extends BaseDirectory {
     maybeDeletePendingFiles();
     while (true) {
       try {
-        String name = IndexFileNames.segmentFileName(prefix, suffix + "_" + Long.toString(nextTempFileCounter.getAndIncrement(), Character.MAX_RADIX), "tmp");
+        String name = getTempFileName(prefix, suffix, nextTempFileCounter.getAndIncrement());
         if (pendingDeletes.contains(name)) {
           continue;
         }
diff --git a/lucene/core/src/java/org/apache/lucene/store/FileSwitchDirectory.java b/lucene/core/src/java/org/apache/lucene/store/FileSwitchDirectory.java
index 7484ae00f56..9552710becf 100644
--- a/lucene/core/src/java/org/apache/lucene/store/FileSwitchDirectory.java
+++ b/lucene/core/src/java/org/apache/lucene/store/FileSwitchDirectory.java
@@ -27,6 +27,8 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import org.apache.lucene.util.IOUtils;
 
@@ -53,8 +55,12 @@ public class FileSwitchDirectory extends Directory {
   private final Directory primaryDir;
   private final Set<String> primaryExtensions;
   private boolean doClose;
+  private static final Pattern EXT_PATTERN = Pattern.compile("\\.([a-zA-Z]+)");
 
   public FileSwitchDirectory(Set<String> primaryExtensions, Directory primaryDir, Directory secondaryDir, boolean doClose) {
+    if (primaryExtensions.contains("tmp")) {
+      throw new IllegalArgumentException("tmp is a reserved extension");
+    }
     this.primaryExtensions = primaryExtensions;
     this.primaryDir = primaryDir;
     this.secondaryDir = secondaryDir;
@@ -141,7 +147,14 @@ public class FileSwitchDirectory extends Directory {
     if (i == -1) {
       return "";
     }
-    return name.substring(i+1, name.length());
+    String ext = name.substring(i + 1);
+    if (ext.equals("tmp")) {
+      Matcher matcher = EXT_PATTERN.matcher(name.substring(0, i + 1));
+      if (matcher.find()) {
+        return matcher.group(1);
+      }
+    }
+    return ext;
   }
 
   private Directory getDirectory(String name) {
@@ -174,7 +187,12 @@ public class FileSwitchDirectory extends Directory {
 
   @Override
   public IndexOutput createTempOutput(String prefix, String suffix, IOContext context) throws IOException {
-    return getDirectory("."+suffix).createTempOutput(prefix, suffix, context);
+    // this is best effort - it's ok to create a tmp file with any prefix and suffix. Yet if this file is then
+    // in-turn used to rename they must match to the same directory hence we use the full file-name to find
+    // the right directory. Here we can't make a decision but we need to ensure that all other operations
+    // map to the right directory.
+    String tmpFileName = getTempFileName(prefix, suffix, 0);
+    return getDirectory(tmpFileName).createTempOutput(prefix, suffix, context);
   }
 
   @Override
@@ -183,10 +201,11 @@ public class FileSwitchDirectory extends Directory {
     List<String> secondaryNames = new ArrayList<>();
 
     for (String name : names)
-      if (primaryExtensions.contains(getExtension(name)))
+      if (primaryExtensions.contains(getExtension(name))) {
         primaryNames.add(name);
-      else
+      } else {
         secondaryNames.add(name);
+      }
 
     primaryDir.sync(primaryNames);
     secondaryDir.sync(secondaryNames);
diff --git a/lucene/core/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java b/lucene/core/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java
index 256ee1b871b..0a12eedc614 100644
--- a/lucene/core/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java
+++ b/lucene/core/src/test/org/apache/lucene/store/TestFileSwitchDirectory.java
@@ -19,6 +19,7 @@ package org.apache.lucene.store;
 
 import java.io.IOException;
 import java.net.URI;
+import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.FileSystem;
 import java.nio.file.Path;
 import java.util.Arrays;
@@ -114,6 +115,32 @@ public class TestFileSwitchDirectory extends BaseDirectoryTestCase {
     dir.close();
   }
 
+  public void testRenameTmpFile() throws IOException {
+    try (Directory directory = getDirectory(createTempDir())) {
+      final String name;
+      try (IndexOutput out = directory.createTempOutput("foo.cfs", "", IOContext.DEFAULT)) {
+        out.writeInt(1);
+        name = out.getName();
+      }
+      assertEquals(1, Arrays.stream(directory.listAll()).filter(f -> f.equals(name)).count());
+      assertEquals(0, Arrays.stream(directory.listAll()).filter(f -> f.equals("foo.cfs")).count());
+      directory.rename(name, "foo.cfs");
+      assertEquals(1, Arrays.stream(directory.listAll()).filter(f -> f.equals("foo.cfs")).count());
+      assertEquals(0, Arrays.stream(directory.listAll()).filter(f -> f.equals(name)).count());
+    }
+
+    try (Directory directory= newFSSwitchDirectory(Collections.singleton("bar"))) {
+      String brokenName;
+      try (IndexOutput out = directory.createTempOutput("foo", "bar", IOContext.DEFAULT)) {
+        out.writeInt(1);
+        brokenName = out.getName();
+      }
+      AtomicMoveNotSupportedException exception = expectThrows(AtomicMoveNotSupportedException.class,
+          () -> directory.rename(brokenName, "foo.bar"));
+      assertEquals("foo_bar_0.tmp -> foo.bar: source and dest are in different directories", exception.getMessage());
+    }
+  }
+
   @Override
   protected Directory getDirectory(Path path) throws IOException {
     Set<String> extensions = new HashSet<String>();
diff --git a/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
index cd8d492ca6f..e5159a784e3 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/util/LuceneTestCase.java
@@ -91,6 +91,7 @@ import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
 import org.apache.lucene.store.FSLockFactory;
+import org.apache.lucene.store.FileSwitchDirectory;
 import org.apache.lucene.store.FlushInfo;
 import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.LockFactory;
@@ -1414,14 +1415,13 @@ public abstract class LuceneTestCase extends Assert {
       }
 
       Directory fsdir = newFSDirectoryImpl(clazz, f, lf);
-// LUCENE-8853: FileSwitchDirectory is broken for tmp outputs.
-//      if (rarely()) {
-//        List<String> fileExtensions =
-//            Arrays.asList("fdt", "fdx", "tim", "tip", "si", "fnm", "pos", "dii", "dim", "nvm", "nvd", "dvm", "dvd");
-//        Collections.shuffle(fileExtensions, random());
-//        fileExtensions = fileExtensions.subList(0, 1 + random().nextInt(fileExtensions.size()));
-//        fsdir = new FileSwitchDirectory(new HashSet<>(fileExtensions), fsdir, newFSDirectoryImpl(clazz, f, lf), true);
-//      }
+      if (rarely()) {
+        List<String> fileExtensions =
+            Arrays.asList("fdt", "fdx", "tim", "tip", "si", "fnm", "pos", "dii", "dim", "nvm", "nvd", "dvm", "dvd");
+        Collections.shuffle(fileExtensions, random());
+        fileExtensions = fileExtensions.subList(0, 1 + random().nextInt(fileExtensions.size()));
+        fsdir = new FileSwitchDirectory(new HashSet<>(fileExtensions), fsdir, newFSDirectoryImpl(clazz, f, lf), true);
+      }
       BaseDirectoryWrapper wrapped = wrapDirectory(random(), fsdir, bare);
       return wrapped;
     } catch (Exception e) {