diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8f51670..dc83483 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,11 +20,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [ "ubuntu-latest", "macos-latest"]
-        python-version: [ "3.6", "3.7", "3.8", "3.9" ]
+        python-version: [ "3.7", "3.8", "3.9", "3.10" ]
 
     steps:
       - name: Cancel previous runs
-        uses: styfle/cancel-workflow-action@0.9.0
+        uses: styfle/cancel-workflow-action@0.9.1
         with:
           access_token: ${{ github.token }}
       - name: Checkout
diff --git a/conda_recipe/meta.yaml b/conda_recipe/meta.yaml
index 060b824..6ed2455 100644
--- a/conda_recipe/meta.yaml
+++ b/conda_recipe/meta.yaml
@@ -1,4 +1,4 @@
-{% set version = "1.3.2.6" %}
+{% set version = "1.3.3" %}
 
 package:
   name: wrf-python
diff --git a/src/wrf/g_slp.py b/src/wrf/g_slp.py
index f422bed..695b62d 100755
--- a/src/wrf/g_slp.py
+++ b/src/wrf/g_slp.py
@@ -63,7 +63,7 @@ def get_slp(wrfin, timeidx=0, method="cat", squeeze=True,
 
         units (:obj:`str`): The desired units.  Refer to the :meth:`getvar`
             product table for a list of available units for 'slp'.  Default
-            is 'Pa'.
+            is 'hPa'.
 
     Returns:
 
diff --git a/src/wrf/projection.py b/src/wrf/projection.py
index 670e67a..e169341 100644
--- a/src/wrf/projection.py
+++ b/src/wrf/projection.py
@@ -76,12 +76,9 @@ if cartopy_enabled():
                 else:
                     xlimits[0] = -xlimits[0]
 
-            self._xlimits = tuple(xlimits)
-            self._ylimits = tuple(limits[..., 1])
-
             # Compatibility with cartopy >= 0.17
-            self._x_limits = self._xlimits
-            self._y_limits = self._ylimits
+            self._x_limits = tuple(xlimits)
+            self._y_limits =  tuple(limits[..., 1])
 
             self._threshold = np.diff(self.x_limits)[0] / 720
 
@@ -824,7 +821,7 @@ class PolarStereographic(WrfProj):
 
     def _proj4(self):
         _proj4 = ("+proj=stere +units=m +a={} +b={} "
-                  "+lat0={} +lon_0={} +lat_ts={} +nadgrids=@null".format(
+                  "+lat_0={} +lon_0={} +lat_ts={} +nadgrids=@null".format(
                                             Constants.WRF_EARTH_RADIUS,
                                             Constants.WRF_EARTH_RADIUS,
                                             self._hemi,