diff --git a/.binder/environment.yml b/.binder/environment.yml
index 46e5eb2..29310f3 100644
--- a/.binder/environment.yml
+++ b/.binder/environment.yml
@@ -8,6 +8,7 @@ dependencies:
   - xarray
   - scipy
   - pandas
+  - polars
   - matplotlib
   - cartopy
   - cmocean
diff --git a/.binder/patch_notebooks.py b/.binder/patch_notebooks.py
new file mode 100644
index 0000000..54dfe0c
--- /dev/null
+++ b/.binder/patch_notebooks.py
@@ -0,0 +1,29 @@
+import json
+import re
+import sys
+
+# `html_str = pio.to_html(fig, ...)` followed by `display(HTML(html_str))`
+PATTERN = re.compile(r"(\w+) = pio\.to_html\((\w+).*\)\ndisplay\(HTML\(\1\)\)")
+
+
+def patch_notebook(nb: dict) -> int:
+    """Patch a notebook dict in place, returning the number of replacements."""
+    n_total = 0
+    for cell in nb["cells"]:
+        if cell["cell_type"] == "code":
+            source, n = PATTERN.subn(r"\2.show()", "".join(cell["source"]))
+            if n:
+                cell["source"] = source.splitlines(keepends=True)
+                cell["outputs"] = []  # stale docs output
+                n_total += n
+    return n_total
+
+
+if __name__ == "__main__":
+    for path in sys.argv[1:]:
+        with open(path, encoding="utf-8") as f:
+            nb = json.load(f)
+        if patch_notebook(nb):
+            with open(path, "w", encoding="utf-8") as f:
+                json.dump(nb, f, indent=1, ensure_ascii=False)
+            print(f"Patched plotly figures -> fig.show() in {path}")
diff --git a/.binder/postBuild b/.binder/postBuild
index 1651f95..2376544 100644
--- a/.binder/postBuild
+++ b/.binder/postBuild
@@ -42,6 +42,11 @@ while IFS= read -r file_path || [ -n "$file_path" ]; do
   fi
 done < "$LIST_FILE"
 
+# swap docs-only plotly HTML embedding for fig.show(), so figures render in Jupyter on Binder
+shopt -s nullglob
+python .binder/patch_notebooks.py "$TARGET_DIR"/*.ipynb
+shopt -u nullglob
+
 # landing page: copy to the workspace root
 cp .binder/welcome.md welcome.md
 
diff --git a/.github/workflows/check-binder-files.yml b/.github/workflows/check-binder-files.yml
index 4d4362d..a930f82 100644
--- a/.github/workflows/check-binder-files.yml
+++ b/.github/workflows/check-binder-files.yml
@@ -6,6 +6,8 @@ on:
     paths:
       - '.binder/files_to_fetch.txt'
       - '.binder/config.yaml'
+      - '.binder/patch_notebooks.py'
+      - 'tests/**'
   pull_request:
     types: [ opened, synchronize, reopened ]
     branches: [ main ]
@@ -31,6 +33,6 @@ jobs:
           python -m pip install --upgrade pip
           pip install pytest pyyaml
 
-      - name: Run notebook URL unit tests
+      - name: Run notebook URL and patch drift unit tests
         run: |
-          pytest tests/test_binder_files.py -v
\ No newline at end of file
+          pytest tests/ -v
\ No newline at end of file
diff --git a/tests/test_binder_patch_notebooks.py b/tests/test_binder_patch_notebooks.py
new file mode 100644
index 0000000..d7a9168
--- /dev/null
+++ b/tests/test_binder_patch_notebooks.py
@@ -0,0 +1,54 @@
+import importlib.util
+import json
+import urllib.request
+from pathlib import Path
+
+import pytest
+
+from test_binder_files import CONFIG, get_target_files
+
+_spec = importlib.util.spec_from_file_location(
+    "patch_notebooks", Path(__file__).parent.parent / ".binder" / "patch_notebooks.py"
+)
+patch_notebooks = importlib.util.module_from_spec(_spec)
+_spec.loader.exec_module(patch_notebooks)
+
+
+def _code(nb):
+    return "\n".join(
+        "".join(c["source"]) for c in nb["cells"] if c["cell_type"] == "code"
+    )
+
+
+def test_patch_notebook():
+    nb = {
+        "cells": [
+            {
+                "cell_type": "code",
+                "source": [
+                    'html_str = pio.to_html(fig, include_plotlyjs="cdn")\n',
+                    "display(HTML(html_str))",
+                ],
+                "outputs": [{"output_type": "display_data"}],
+            }
+        ]
+    }
+    assert patch_notebooks.patch_notebook(nb) == 1
+    assert nb["cells"][0]["source"] == ["fig.show()"]
+    assert nb["cells"][0]["outputs"] == []
+
+
+@pytest.mark.parametrize("file_path", get_target_files())
+def test_upstream_notebook_fully_patched(file_path):
+    """Catch drift: any plotly HTML embedding upstream must be rewritten by the patch."""
+    url = (
+        f"https://raw.githubusercontent.com/{CONFIG['repo_owner']}/"
+        f"{CONFIG['repo_name']}/{CONFIG['branch']}/{file_path}"
+    )
+    with urllib.request.urlopen(url) as response:
+        nb = json.load(response)
+    patch_notebooks.patch_notebook(nb)
+    assert "to_html(" not in _code(nb), (
+        f"{file_path} embeds plotly HTML in a way .binder/patch_notebooks.py doesn't "
+        "rewrite to `fig.show()`, so it won't render on Binder. Update PATTERN."
+    )