diff --git a/doc/examples/monthly-means.rst b/doc/examples/monthly-means.rst
index 7cc47eb2847..7d620f1bca3 100644
--- a/doc/examples/monthly-means.rst
+++ b/doc/examples/monthly-means.rst
@@ -83,7 +83,7 @@ the ``calendar.month_range`` function.
 
         for i, (month, year) in enumerate(zip(time.month, time.year)):
             month_length[i] = cal_days[month]
-            if leap_year(year, calendar=calendar):
+            if leap_year(year, calendar=calendar) and month == 2:
                 month_length[i] += 1
         return month_length
 
diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 6bcf4b61436..6c69d8014d9 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -73,7 +73,7 @@ Bug fixes
 
 Documentation
 ~~~~~~~~~~~~~
-
+- Fix leap year condition in example (http://xarray.pydata.org/en/stable/examples/monthly-means.html) by `Mickaël Lalande <https://github.com/mickaellalande>`_.
 - Fix the documentation of :py:meth:`DataArray.resample` and
   :py:meth:`Dataset.resample` and explicitly state that a
   datetime-like dimension is required. (:pull:`3400`)