Revert "Re-enable parallel builds in CI"
diff --git a/.circleci/setup_env.sh b/.circleci/setup_env.sh
index 7f82b613f8cb8..52a8cab1cd2de 100755
--- a/.circleci/setup_env.sh
+++ b/.circleci/setup_env.sh
@@ -55,7 +55,8 @@ if pip list | grep -q ^pandas; then
 fi
 
 echo "Build extensions"
-python setup.py build_ext -q -j4
+# GH 47305: Parallel build can causes flaky ImportError from pandas/_libs/tslibs
+python setup.py build_ext -q -j1
 
 echo "Install pandas"
 python -m pip install --no-build-isolation --no-use-pep517 -e .
diff --git a/.github/workflows/32-bit-linux.yml b/.github/workflows/32-bit-linux.yml
index e14be521ff523..4e363c7fd573d 100644
--- a/.github/workflows/32-bit-linux.yml
+++ b/.github/workflows/32-bit-linux.yml
@@ -42,7 +42,7 @@ jobs:
           python -m pip install --no-deps -U pip wheel 'setuptools<60.0.0' && \
           python -m pip install versioneer[toml] && \
           python -m pip install cython numpy python-dateutil pytz pytest>=7.0.0 pytest-xdist>=2.2.0 pytest-asyncio>=0.17 hypothesis>=6.34.2 && \
-          python setup.py build_ext -q -j$(nproc) && \
+          python setup.py build_ext -q -j1 && \
           python -m pip install --no-build-isolation --no-use-pep517 -e . && \
           python -m pip list && \
           export PANDAS_CI=1 && \
diff --git a/.github/workflows/python-dev.yml b/.github/workflows/python-dev.yml
index 5730e2b75f48f..910b68dce07d0 100644
--- a/.github/workflows/python-dev.yml
+++ b/.github/workflows/python-dev.yml
@@ -82,9 +82,10 @@ jobs:
         python -m pip install python-dateutil pytz cython hypothesis>=6.34.2 pytest>=7.0.0 pytest-xdist>=2.2.0 pytest-cov pytest-asyncio>=0.17
         python -m pip list
 
+    # GH 47305: Parallel build can cause flaky ImportError from pandas/_libs/tslibs
     - name: Build Pandas
       run: |
-        python setup.py build_ext -q -j4
+        python setup.py build_ext -q -j1
         python -m pip install -e . --no-build-isolation --no-use-pep517 --no-index
 
     - name: Build Version

Reverts pandas-dev/pandas#51902

Depends on #51525 which is reverted by #51951