diff --git a/.github/workflows/tarball-tests.yml b/.github/workflows/tarball-tests.yml
new file mode 100644
index 0000000..3a4ffde
--- /dev/null
+++ b/.github/workflows/tarball-tests.yml
@@ -0,0 +1,34 @@
+name: Tarball tests
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Conda
+      uses: s-weigand/setup-conda@v1
+      with:
+        activate-conda: false
+        conda-channels: conda-forge
+
+    - name: Create environment
+      shell: bash -l {0}
+      run: |
+        conda create --name TEST python=3 python-build cython numpy --file requirements-dev.txt
+        source activate TEST
+        conda info --all
+        conda list
+
+    - name: Tarball
+      shell: bash -l {0}
+      run: |
+        source activate TEST
+        python -m build --skip-dependencies --sdist --wheel .
+        check-manifest --verbose
+        twine check dist/*
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..beddb8e
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,45 @@
+name: Tests
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  run:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        python-version: ["3.7", "3.8", "3.9"]
+        os: [windows-latest, ubuntu-latest, macos-latest]
+        # Oldest one based on NEP-29 and latest one.
+        # See https://numpy.org/neps/nep-0029-deprecation_policy.html
+        numpy-version: ["1.17", "1.20"]
+        exclude:
+          - python-version: "3.9"
+            numpy-version: "1.17"
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Conda
+      uses: s-weigand/setup-conda@v1
+      with:
+        activate-conda: false
+        conda-channels: conda-forge
+
+    - name: Python ${{ matrix.python-version }} numpy ${{ matrix.numpy-version }}
+      shell: bash -l {0}
+      run: |
+        conda create --name TEST python=${{ matrix.python-version }} python-build cython numpy=${{ matrix.numpy-version }} --file requirements-dev.txt
+        source activate TEST
+        pip install -e . --no-deps --force-reinstall
+        conda info --all
+        conda list
+
+    - name: Tests
+      shell: bash -l {0}
+      run: |
+        source activate TEST
+        python -c "import numpy; print(f'Running numpy {numpy.__version__}')"
+        pytest -s -rxs -v gsw/tests
diff --git a/.travis.yml b/.travis.yml
index bdc8b78..a193960 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,18 +9,8 @@ env:
 matrix:
   fast_finish: true
   include:
-  - name: "py37-np116"
-    env: PY=3.7 NUMPY=1.16
-  - name: "py37-np119"
-    env: PY=3.7 NUMPY=1.19
-  - name: "py38-np116"
-    env: PY=3.8 NUMPY=1.16
-  - name: "py38-np119"
-    env: PY=3.8 NUMPY=1.19
   - name: "docs"
     env: NUMPY=1 PY=3
-  - name: "tarball"
-    env: NUMPY=1 PY=3
 
 before_install:
   # Install miniconda and create TEST env.
@@ -44,21 +34,6 @@ install:
   - pip install -e . --no-deps --force-reinstall
 
 script:
-  - |
-    if [[ $TRAVIS_JOB_NAME == 'tarball' ]]; then
-      python -m pep517.build --source --binary . --out-dir dist
-      check-manifest --verbose
-      twine check dist/*
-    fi
-
-  - |
-    if [[ $TRAVIS_JOB_NAME == py* ]]; then
-      cp -r gsw/tests /tmp
-      pushd /tmp
-      pytest -s -rxs -v tests
-      popd
-    fi
-
   - |
     if [[ $TRAVIS_JOB_NAME == 'docs' ]]; then
       pushd docs
@@ -71,18 +46,3 @@ script:
         python -m doctr deploy --build-tags --key-path github_deploy_key.enc --built-docs docs/_build/html .
       fi
     fi
-
-
-deploy:
-  skip_cleanup: true
-  provider: pypi
-  user: ocefpaf
-  password:
-    secure: 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
-  distributions: sdist
-  upload_docs: no
-  on:
-    repo: TEOS-10/GSW-Python
-    tags: true
-    all_branches: master
-    condition: '$TRAVIS_JOB_NAME == "deploy"'
diff --git a/pyproject.toml b/pyproject.toml
index 70dccb2..95051bd 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,3 @@
 [build-system]
-requires = ["pip >9.0.1", "setuptools>=42", "wheel", "setuptools_scm[toml]>=3.4", "cython", "numpy"]
+requires = ["pip >9.0.1", "setuptools>=42", "wheel", "setuptools_scm[toml]>=3.4", "cython", "oldest-supported-numpy", "build"]
 build-backend = "setuptools.build_meta"
diff --git a/requirements-dev.txt b/requirements-dev.txt
index f48dff3..7ba2df0 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -6,3 +6,5 @@ setuptools_scm
 sphinx
 sphinx_rtd_theme
 twine
+xarray
+dask