diff --git a/.github/workflows/gapic-generator-tests.yml b/.github/workflows/gapic-generator-tests.yml
index 68499e9f8d10..9fd13ea59309 100644
--- a/.github/workflows/gapic-generator-tests.yml
+++ b/.github/workflows/gapic-generator-tests.yml
@@ -362,7 +362,7 @@ jobs:
           persist-credentials: false
       - name: Cache Bazel files
         id: cache-bazel
-        uses: actions/cache@caa296126883cff596d87d8935842f9db880ef25 # v5
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6
         with:
           path: ~/.cache/bazel
           # Ensure CACHE_VERSION is defined in the mono-repo secrets!
diff --git a/.github/workflows/prerelease-deps.yml b/.github/workflows/prerelease-deps.yml
index c9ae26cd4314..4001686497c7 100644
--- a/.github/workflows/prerelease-deps.yml
+++ b/.github/workflows/prerelease-deps.yml
@@ -64,7 +64,7 @@ jobs:
           allow-prereleases: true
 
       - name: Cache pip wheels (including compiled source builds)
-        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4
+        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6
         with:
           path: ~/.cache/pip
           # Save a fresh cache snapshot for each run so newly compiled wheels are persisted
diff --git a/packages/db-dtypes/noxfile.py b/packages/db-dtypes/noxfile.py
index e4f43fa955f6..bf8068d9c330 100644
--- a/packages/db-dtypes/noxfile.py
+++ b/packages/db-dtypes/noxfile.py
@@ -265,6 +265,11 @@ def prerelease(session, tests_path):
         "pytest",
         "pytest-cov",
         "pytest-asyncio",
+        # tzdata is only needed for testing: pandas 3.0+ no longer installs
+        # tzdata by default on Linux, and compliance tests import
+        # pandas.tests.extension.base (which loads pandas.conftest and
+        # initializes a "US/Pacific" date_range via zoneinfo).
+        "tzdata",
         "-c",
         constraints_path,
     )