diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index c53188f65..3e813fb62 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -38,12 +38,30 @@ x_defaults:
       - "-//test:output_file_map_default"
   windows_common: &windows_common
     platform: windows
+    environment:
+      SWIFT_VERSION: 0.0.0
+      CC: "clang-cl"
+      PATH: "%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr\\bin;%LOCALAPPDATA%\\Programs\\Swift\\Runtimes\\%SWIFT_VERSION%\\usr\\bin;%PATH%"
+      SDKROOT: "%LOCALAPPDATA%\\Programs\\Swift\\Platforms\\%SWIFT_VERSION%\\Windows.platform\\Developer\\SDKs\\Windows.sdk"
+      BAZEL_LLVM: "%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr"
     build_flags:
       # Override 'sandboxed' strategy set in .bazelrc because it's not
       # available on Windows
       - "--strategy=SwiftCompile="
+      - "--compiler=clang-cl"
+      # TODO: Use the new way of setting toolchains.
+      - "--noincompatible_enable_cc_toolchain_resolution"
     build_targets:
       - "//tools/..."
+    test_flags:
+      - "--compiler=clang-cl"
+      # TODO: Use the new way of setting toolchains.
+      - "--noincompatible_enable_cc_toolchain_resolution"
+    test_targets:
+      - "//examples/..."
+      - "-//examples/apple/..."
+      # TODO: Fix gRPC on Windows
+      - "-//examples/xplatform/grpc/..."
 
 tasks:
   macos_6:
@@ -120,11 +138,14 @@ tasks:
       - .bazelci/update_workspace_to_deps_heads.sh
     <<: *linux_common
 
-  # TODO: re-enable when Windows in Bazel CI is properly configured for Swift.
-  # windows_last_green:
-  #   name: "Last Green Bazel"
-  #   bazel: last_green
-  #   <<: *windows_common
+  windows_last_green:
+    name: "Last Green Bazel"
+    bazel: last_green
+    batch_commands:
+      - echo --- Downloading and installing Swift %SWIFT_VERSION%
+      - curl.exe -L https://download.swift.org/swift-5.10-branch/windows10/swift-5.10-DEVELOPMENT-SNAPSHOT-2024-01-18-a/swift-5.10-DEVELOPMENT-SNAPSHOT-2024-01-18-a-windows10.exe -o %TEMP%\installer.exe
+      - PowerShell Start-Process -FilePath ${env:TEMP}\installer.exe -ArgumentList(\"/install\", \"/passive\", \"/norestart\", \"/log log.txt\") -Wait -PassThru -Verb RunAs
+    <<: *windows_common
 
   doc_tests:
     name: "Doc tests"
diff --git a/swift/internal/swift_autoconfiguration.bzl b/swift/internal/swift_autoconfiguration.bzl
index 6ec8ced15..6c301dd01 100644
--- a/swift/internal/swift_autoconfiguration.bzl
+++ b/swift/internal/swift_autoconfiguration.bzl
@@ -368,7 +368,7 @@ def _create_windows_toolchain(repository_ctx):
 
     env = {
         "Path": repository_ctx.os.environ["Path"] if "Path" in repository_ctx.os.environ else repository_ctx.os.environ["PATH"],
-        "ProgramData": repository_ctx.os.environ["ProgramData"],
+        "ProgramData": repository_ctx.os.environ["ProgramData"] if "ProgramData" in repository_ctx.os.environ else repository_ctx.os.environ["PROGRAMDATA"],
     }
 
     repository_ctx.file(
diff --git a/swift/toolchains/swift_toolchain.bzl b/swift/toolchains/swift_toolchain.bzl
index 64a8e2bbb..d5adee666 100644
--- a/swift/toolchains/swift_toolchain.bzl
+++ b/swift/toolchains/swift_toolchain.bzl
@@ -421,7 +421,8 @@ def _swift_toolchain_impl(ctx):
     if "clang" not in cc_toolchain.compiler:
         fail("Swift requires the configured CC toolchain to be LLVM (clang). " +
              "Either use the locally installed LLVM by setting `CC=clang` in your environment " +
-             "before invoking Bazel, or configure a Bazel LLVM CC toolchain.")
+             "before invoking Bazel, or configure a Bazel LLVM CC toolchain. " +
+             "Found compiler is %s." % cc_toolchain.compiler)
 
     if ctx.attr.os == "windows":
         swift_linkopts_cc_info = _swift_windows_linkopts_cc_info(
@@ -505,7 +506,7 @@ def _swift_toolchain_impl(ctx):
         xctest = paths.normalize(paths.join(ctx.attr.sdkroot, "..", "..", "Library", "XCTest-{}".format(ctx.attr.xctest_version), "usr", bindir))
         env = dicts.add(
             ctx.attr.env,
-            {"Path": xctest + ";" + ctx.attr.env["Path"]},
+            {"Path": xctest + ";" + ctx.attr.env["PATH"]},
         )
     else:
         env = ctx.attr.env