diff --git a/meteostat/__init__.py b/meteostat/__init__.py
index 6a940f7..6bdbbf5 100644
--- a/meteostat/__init__.py
+++ b/meteostat/__init__.py
@@ -12,7 +12,7 @@
 """
 
 __appname__ = 'meteostat'
-__version__ = '1.5.7'
+__version__ = '1.5.8'
 
 from .interface.base import Base
 from .interface.timeseries import Timeseries
diff --git a/meteostat/interface/normals.py b/meteostat/interface/normals.py
index 9aef7dd..719a6e4 100644
--- a/meteostat/interface/normals.py
+++ b/meteostat/interface/normals.py
@@ -302,7 +302,7 @@ def fetch(self) -> pd.DataFrame:
         temp = copy(self._data)
 
         # Add avg. temperature column
-        temp.insert(0, 'tavg', temp[['tmin', 'tmax']].mean(
+        temp.insert(0, 'tavg', temp[['tmin', 'tmax']].dropna(how='any').mean(
             axis=1).round(1))
 
         # Remove station index if it's a single station
diff --git a/setup.py b/setup.py
index f76dc52..31de62a 100644
--- a/setup.py
+++ b/setup.py
@@ -15,7 +15,7 @@
 # Setup
 setup(
     name='meteostat',
-    version='1.5.7',
+    version='1.5.8',
     author='Meteostat',
     author_email='info@meteostat.net',
     description='Access and analyze historical weather and climate data with Python.',