diff --git a/docs/sphinx/source/whatsnew/v0.9.2.rst b/docs/sphinx/source/whatsnew/v0.9.2.rst
index dcce33370f..aebb65acba 100644
--- a/docs/sphinx/source/whatsnew/v0.9.2.rst
+++ b/docs/sphinx/source/whatsnew/v0.9.2.rst
@@ -24,6 +24,10 @@ Bug fixes
   where passing localized timezones with large UTC offsets could return
   rise/set/transit times for the wrong day in recent versions of ``ephem``
   (:issue:`1449`, :pull:`1448`)
+* :py:func:`pvlib.iotools.get_psm3` now raises a deprecation warning if
+  the `leap_day` parameter is not specified in a single-year request.
+  Starting in pvlib 0.11.0 `leap_day` will default to True instead of False.
+  (:issue:`1481`, :pull:`1511`)
 
 
 Testing
diff --git a/pvlib/iotools/psm3.py b/pvlib/iotools/psm3.py
index a8f9781c22..71e74dfd54 100644
--- a/pvlib/iotools/psm3.py
+++ b/pvlib/iotools/psm3.py
@@ -42,7 +42,7 @@
 
 
 def get_psm3(latitude, longitude, api_key, email, names='tmy', interval=60,
-             attributes=ATTRIBUTES, leap_day=False, full_name=PVLIB_PYTHON,
+             attributes=ATTRIBUTES, leap_day=None, full_name=PVLIB_PYTHON,
              affiliation=PVLIB_PYTHON, map_variables=None, timeout=30):
     """
     Retrieve NSRDB PSM3 timeseries weather data from the PSM3 API. The NSRDB
@@ -165,6 +165,14 @@ def get_psm3(latitude, longitude, api_key, email, names='tmy', interval=60,
     attributes = [amap.get(a, a) for a in attributes]
     attributes = list(set(attributes))  # remove duplicate values
 
+    if (leap_day is None) and (not names.startswith('t')):
+        warnings.warn(
+            'The ``get_psm3`` function will default to leap_day=True '
+            'starting in pvlib 0.11.0. Specify leap_day=True '
+            'to enable this behavior now, or specify leap_day=False '
+            'to hide this warning.', pvlibDeprecationWarning)
+        leap_day = False
+
     # required query-string parameters for request to PSM3 API
     params = {
         'api_key': api_key,
diff --git a/pvlib/tests/iotools/test_psm3.py b/pvlib/tests/iotools/test_psm3.py
index d151cfa6da..c02246c5bd 100644
--- a/pvlib/tests/iotools/test_psm3.py
+++ b/pvlib/tests/iotools/test_psm3.py
@@ -78,7 +78,7 @@ def test_get_psm3_tmy(nrel_api_key):
     """test get_psm3 with a TMY"""
     data, metadata = psm3.get_psm3(LATITUDE, LONGITUDE, nrel_api_key,
                                    PVLIB_EMAIL, names='tmy-2017',
-                                   map_variables=False)
+                                   leap_day=False, map_variables=False)
     expected = pd.read_csv(TMY_TEST_DATA)
     assert_psm3_equal(data, metadata, expected)
 
@@ -89,7 +89,8 @@ def test_get_psm3_singleyear(nrel_api_key):
     """test get_psm3 with a single year"""
     data, metadata = psm3.get_psm3(LATITUDE, LONGITUDE, nrel_api_key,
                                    PVLIB_EMAIL, names='2017',
-                                   map_variables=False, interval=30)
+                                   leap_day=False,  map_variables=False,
+                                   interval=30)
     expected = pd.read_csv(YEAR_TEST_DATA)
     assert_psm3_equal(data, metadata, expected)
 
@@ -100,7 +101,7 @@ def test_get_psm3_5min(nrel_api_key):
     """test get_psm3 for 5-minute data"""
     data, metadata = psm3.get_psm3(LATITUDE, LONGITUDE, nrel_api_key,
                                    PVLIB_EMAIL, names='2019', interval=5,
-                                   map_variables=False)
+                                   leap_day=False, map_variables=False)
     assert len(data) == 525600/5
     first_day = data.loc['2019-01-01']
     expected = pd.read_csv(YEAR_TEST_DATA_5MIN)
@@ -137,7 +138,8 @@ def test_get_psm3_tmy_errors(
     """
     with pytest.raises(HTTPError) as excinfo:
         psm3.get_psm3(latitude, longitude, api_key, PVLIB_EMAIL,
-                      names=names, interval=interval, map_variables=False)
+                      names=names, interval=interval, leap_day=False,
+                      map_variables=False)
     # ensure the HTTPError caught isn't due to overuse of the API key
     assert "OVER_RATE_LIMIT" not in str(excinfo.value)
 
@@ -186,7 +188,7 @@ def test_get_psm3_attribute_mapping(nrel_api_key):
     data, meta = psm3.get_psm3(LATITUDE, LONGITUDE, nrel_api_key, PVLIB_EMAIL,
                                names=2019, interval=60,
                                attributes=['ghi', 'wind_speed'],
-                               map_variables=True)
+                               leap_day=False, map_variables=True)
     assert 'ghi' in data.columns
     assert 'wind_speed' in data.columns
     assert 'latitude' in meta.keys()
@@ -199,3 +201,14 @@ def test_get_psm3_attribute_mapping(nrel_api_key):
 def test_psm3_variable_map_deprecation_warning(nrel_api_key):
     with pytest.warns(pvlibDeprecationWarning, match='names will be renamed'):
         _ = psm3.read_psm3(MANUAL_TEST_DATA)
+
+
+@pytest.mark.remote_data
+@pytest.mark.flaky(reruns=RERUNS, reruns_delay=RERUNS_DELAY)
+def test_psm3_leap_day_deprecation_warning(nrel_api_key):
+    with pytest.warns(pvlibDeprecationWarning,
+                      match='default to leap_day=True'):
+        _, _ = psm3.get_psm3(LATITUDE, LONGITUDE, nrel_api_key, PVLIB_EMAIL,
+                             names=2019, interval=60,
+                             attributes=['ghi', 'wind_speed'],
+                             map_variables=True)