diff --git a/docs/conf.py b/docs/conf.py
index 044dc0d49..e67cadd0a 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -59,7 +59,7 @@
                        'python': ('https://docs.python.org/3/', None),
                        'numpy': ('https://docs.scipy.org/doc/numpy/', None),
                        'matplotlib': ('https://matplotlib.org', None),
-                       'requests': ('https://2.python-requests.org/en/master/', None),
+                       'requests': ('https://requests.kennethreitz.org/en/master/', None),
                        }
 
 # Add any paths that contain templates here, relative to this directory.
diff --git a/examples/ndbc/buoy_met_request.py b/examples/ndbc/buoy_met_request.py
index 1264ee21e..9b1303f06 100644
--- a/examples/ndbc/buoy_met_request.py
+++ b/examples/ndbc/buoy_met_request.py
@@ -16,7 +16,7 @@
 ####################################################
 # Get a pandas data frame of all of the observations, meteorological data is the default
 # observation set to query.
-df = NDBC.realtime_observations('41002')
+df = NDBC.realtime_observations('46006')
 df.head()
 
 ####################################################
diff --git a/siphon/catalog.py b/siphon/catalog.py
index bc8273111..b4b1039d7 100644
--- a/siphon/catalog.py
+++ b/siphon/catalog.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2013-2017 Siphon Contributors.
+# Copyright (c) 2013-2019 Siphon Contributors.
 # Distributed under the terms of the BSD 3-Clause License.
 # SPDX-License-Identifier: BSD-3-Clause
 """
@@ -11,6 +11,7 @@
 from datetime import datetime
 import logging
 import re
+import warnings
 import xml.etree.ElementTree as ET  # noqa:N814
 try:
     from urlparse import urljoin, urlparse
@@ -146,6 +147,9 @@ def filter_time_range(self, start, end, regex=None, strptime=None):
             All values corresponding to times within the specified range
 
         """
+        if start > end:
+            warnings.warn('The provided start time comes after the end time. No data will '
+                          'be returned.', UserWarning)
         return [item[-1] for item in self._get_datasets_with_times(regex, strptime)
                 if start <= item[0] <= end]
 
diff --git a/siphon/http_util.py b/siphon/http_util.py
index 525d58305..9633df7d5 100644
--- a/siphon/http_util.py
+++ b/siphon/http_util.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2013-2015 Siphon Contributors.
+# Copyright (c) 2013-2019 Siphon Contributors.
 # Distributed under the terms of the BSD 3-Clause License.
 # SPDX-License-Identifier: BSD-3-Clause
 """Utility code to support making requests using HTTP."""
@@ -8,6 +8,7 @@
 from io import BytesIO
 from itertools import chain
 import posixpath
+import warnings
 try:
     from urllib.parse import urlencode, urljoin  # noqa
 except ImportError:
@@ -317,6 +318,9 @@ def time_range(self, start, end):
             Returns self for chaining calls
 
         """
+        if start > end:
+            warnings.warn('The provided start time comes after the end time. No data will '
+                          'be returned.', UserWarning)
         self._set_query(self.time_query, time_start=self._format_time(start),
                         time_end=self._format_time(end))
         return self
diff --git a/siphon/tests/test_catalog.py b/siphon/tests/test_catalog.py
index 54f1ab2cd..98747070b 100644
--- a/siphon/tests/test_catalog.py
+++ b/siphon/tests/test_catalog.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2013-2017 Siphon Contributors.
+# Copyright (c) 2013-2019 Siphon Contributors.
 # Distributed under the terms of the BSD 3-Clause License.
 # SPDX-License-Identifier: BSD-3-Clause
 """Test the catalog access API."""
@@ -232,6 +232,18 @@ def test_datasets_time_range():
                       'NAM_CONUS_20km_noaaport_20150529_0000.grib1']
 
 
+@recorder.use_cassette('top_level_20km_rap_catalog')
+def test_datasets_bad_time_range():
+    """Test warning message for bad time range."""
+    with pytest.warns(UserWarning):
+        url = ('http://thredds.ucar.edu/thredds/catalog/grib/NCEP/NAM/'
+               'CONUS_20km/noaaport/catalog.xml')
+        cat = TDSCatalog(url)
+        in_range = cat.catalog_refs.filter_time_range(datetime(2015, 5, 29, 0),
+                                                      datetime(2015, 5, 28, 0))
+        assert in_range == []
+
+
 @recorder.use_cassette('top_level_20km_rap_catalog')
 def test_datasets_time_range_regex():
     """Test getting datasets by time range using filenames, with manual regex."""
diff --git a/siphon/tests/test_http_util.py b/siphon/tests/test_http_util.py
index 460d5ab04..579d37de4 100644
--- a/siphon/tests/test_http_util.py
+++ b/siphon/tests/test_http_util.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2013-2015 Siphon Contributors.
+# Copyright (c) 2013-2019 Siphon Contributors.
 # Distributed under the terms of the BSD 3-Clause License.
 # SPDX-License-Identifier: BSD-3-Clause
 """Test Siphon's base HTTP helper functionality."""
@@ -102,6 +102,14 @@ def test_data_query_time_format():
     assert query == 'time=2015-06-15T12%3A00%3A00'
 
 
+def test_data_query_bad_time_range():
+    """Test that time queries are properly formatted."""
+    with pytest.warns(UserWarning):
+        dt = datetime(2015, 6, 15, 12, 0, 0)
+        dt2 = datetime(2015, 6, 14, 12, 0, 0)
+        DataQuery().time_range(dt, dt2)
+
+
 def test_data_query_spatial_reset():
     """Test that spatial queries reset each other."""
     dr = DataQuery().lonlat_box(1, 2, 3, 4).lonlat_point(-1, -2)