diff --git a/.github/workflows/pytest-with-coverage.yaml b/.github/workflows/pytest-with-coverage.yaml
index e967e747..51ae62a1 100644
--- a/.github/workflows/pytest-with-coverage.yaml
+++ b/.github/workflows/pytest-with-coverage.yaml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ '3.11', '3.12' ]
+        python-version: [ '3.11', '3.12', '3.13' ]
     uses: UBC-MOAD/gha-workflows/.github/workflows/pytest-with-coverage.yaml@main
     with:
       python-version: ${{ matrix.python-version }}
diff --git a/SalishSeaTools/docs/pkg_development.rst b/SalishSeaTools/docs/pkg_development.rst
index 6a8a1982..e9a9473d 100644
--- a/SalishSeaTools/docs/pkg_development.rst
+++ b/SalishSeaTools/docs/pkg_development.rst
@@ -16,26 +16,25 @@
 
 .. _SalishSeaToolsPackageDevelopment:
 
-*****************************************
-:kbd:`SalishSeaTools` Package Development
-*****************************************
+********************************************
+:py:obj:`SalishSeaTools` Package Development
+********************************************
 
 .. _SalishSeaToolsPythonVersions:
 
 Python Versions
 ===============
 
-The :kbd:`SalishSeaTools` package is developed and tested using `Python`_ 3.9.
-The package uses some Python language features that are not available in versions prior to 3.6,
-in particular:
+.. image:: https://img.shields.io/python/required-version-toml?tomlFilePath=https://raw.githubusercontent.com/SalishSeaCast/SalishSeaCmd/main/pyproject.toml&logo=Python&logoColor=gold&label=Python
+    :target: https://docs.python.org/3
+    :alt: Python Version from PEP 621 TOML
 
-* `formatted string literals`_
-  (aka *f-strings*)
-* the `file system path protocol`_
+The :py:obj:`SalishSeaTools` package is developed using `Python`_ 3.13.
+The minimum supported Python version is 3.11.
+The :ref:`SalishSeaToolsContinuousIntegration` workflow on GitHub ensures that the package
+is tested for all versions of Python>=3.11.
 
 .. _Python: https://www.python.org/
-.. _formatted string literals: https://docs.python.org/3/reference/lexical_analysis.html#f-strings
-.. _file system path protocol: https://docs.python.org/3/whatsnew/3.6.html#whatsnew36-pep519
 
 
 .. _SalishSeaToolsGettingTheCode:
diff --git a/SalishSeaTools/envs/environment-dev.yaml b/SalishSeaTools/envs/environment-dev.yaml
index 1468d85c..28b329d5 100644
--- a/SalishSeaTools/envs/environment-dev.yaml
+++ b/SalishSeaTools/envs/environment-dev.yaml
@@ -36,7 +36,7 @@ dependencies:
   - openpyxl
   - pandas
   - pip
-  - python=3.12
+  - python=3.13
   - pytz
   - python-dateutil
   - pyyaml
diff --git a/SalishSeaTools/envs/requirements.txt b/SalishSeaTools/envs/requirements.txt
index 445c20fc..83fd983f 100644
--- a/SalishSeaTools/envs/requirements.txt
+++ b/SalishSeaTools/envs/requirements.txt
@@ -9,7 +9,7 @@
 
 alabaster==1.0.0
 angles==2.0
-anyio==4.7.0
+anyio==4.8.0
 argon2-cffi==23.1.0
 argon2-cffi-bindings==21.2.0
 arrow==1.3.0
@@ -29,7 +29,7 @@ certifi==2024.12.14
 cffi==1.17.1
 cfgv==3.3.1
 cftime==1.6.4
-charset-normalizer==3.4.0
+charset-normalizer==3.4.1
 click==8.1.8
 cliff==4.8.0
 cmd2==2.5.8
@@ -68,11 +68,11 @@ httpcore==1.0.7
 httpx==0.28.1
 hyperframe==6.0.1
 hyperlink==21.0.0
-identify==2.6.4
+identify==2.6.5
 idna==3.10
 imagesize==1.4.1
 importlib_metadata==8.5.0
-importlib_resources==6.4.5
+importlib_resources==6.5.2
 iniconfig==2.0.0
 ipdb==0.13.13
 ipykernel==6.29.5
@@ -92,7 +92,7 @@ jupyter_client==8.6.3
 jupyter_core==5.7.2
 jupyter-events==0.11.0
 jupyter-lsp==2.2.5
-jupyter_server==2.14.2
+jupyter_server==2.15.0
 jupyter_server_terminals==0.5.3
 jupyterlab==4.3.4
 jupyterlab_pygments==0.3.0
@@ -105,12 +105,12 @@ MarkupSafe==3.0.2
 matplotlib==3.10.0
 matplotlib-inline==0.1.7
 mdurl==0.1.2
-mistune==3.0.2
+mistune==3.1.0
 more-itertools==10.5.0
 munkres==1.1.4
 mypy_extensions==1.0.0
-nbclient==0.10.1
-nbconvert==7.16.4
+nbclient==0.10.2
+nbconvert==7.16.5
 nbformat==5.10.4
 nbsphinx==0.9.5
 nest_asyncio==1.6.0
@@ -128,7 +128,7 @@ pathspec==0.12.1
 pbr==6.1.0
 pexpect==4.9.0
 pickleshare==0.7.5
-pillow==11.0.0
+pillow==11.1.0
 pip==24.3.1
 pkgutil_resolve_name==1.3.10
 platformdirs==4.3.6
@@ -137,12 +137,12 @@ pre_commit==4.0.1
 prettytable==3.12.0
 prometheus_client==0.21.1
 prompt_toolkit==3.0.48
-psutil==6.1.0
+psutil==6.1.1
 ptyprocess==0.7.0
 pure_eval==0.2.3
 pycparser==2.22
-Pygments==2.18.0
-pyparsing==3.2.0
+Pygments==2.19.1
+pyparsing==3.2.1
 pyperclip==1.9.0
 PySide6==6.8.1
 PySocks==1.7.1
@@ -161,7 +161,7 @@ rfc3339_validator==0.1.4
 rfc3986-validator==0.1.1
 rich==13.9.4
 rpds-py==0.22.3
-SalishSeaTools==24.1.dev0
+SalishSeaTools==25.1.dev0
 scipy==1.15.0
 SecretStorage==3.3.3
 Send2Trash==1.8.3
@@ -198,16 +198,14 @@ typing_extensions==4.12.2
 typing_utils==0.1.0
 tzdata==2024.2
 ukkonen==1.0.1
-unicodedata2==15.1.0
 uri-template==1.3.0
-urllib3==2.2.3
+urllib3==2.3.0
 userpath==1.9.2
 virtualenv==20.28.1
 wcwidth==0.2.13
 webcolors==24.11.1
 webencodings==0.5.1
 websocket-client==1.8.0
-wheel==0.45.1
-xarray==2025.1.0
+xarray==2025.1.1
 zipp==3.21.0
 zstandard==0.23.0
diff --git a/docs/breaking_changes.rst b/docs/breaking_changes.rst
index 0809a6c2..3f4c8708 100644
--- a/docs/breaking_changes.rst
+++ b/docs/breaking_changes.rst
@@ -22,6 +22,18 @@
 Changes That Break Backward Compatibility
 *****************************************
 
+.. _BreakingChangesVersion25.1:
+
+Version 25.1 (unreleased)
+=========================
+
+The following changes that were introduced in version 25.1 of the ``tools`` repository
+are incompatible with earlier versions:
+
+* The minimum supported version of Python is 3.11.
+  Development of the :py:obj:`SalishSeaTools` package is done using Python 3.13.
+
+
 .. _BreakingChangesVersion24.1:
 
 Version 24.1 (2025-01-09)
diff --git a/environment-rtd.yaml b/environment-rtd.yaml
index db65d162..b7c3d77e 100644
--- a/environment-rtd.yaml
+++ b/environment-rtd.yaml
@@ -12,7 +12,7 @@ dependencies:
   - jupyter
   - matplotlib
   - pip
-  - python=3.12
+  - python=3.13
 
   # Sphinx and extensions we use
   - nbsphinx==0.9.5