diff --git a/my/bluemaestro/__init__.py b/my/bluemaestro/__init__.py
index 5230431..172164a 100755
--- a/my/bluemaestro/__init__.py
+++ b/my/bluemaestro/__init__.py
@@ -36,6 +36,7 @@ class Measurement(NamedTuple):
 # NOTE: the timezone should be set with respect to the export date!!!
 import pytz # type: ignore
 tz = pytz.timezone('Europe/London')
+# TODO when I change tz, check the diff
 
 
 @mcachew(cache_path=cache_dir() / 'bluemaestro.cache')
diff --git a/my/body/sleep/common.py b/my/body/sleep/common.py
index 81879fe..0b6fa1c 100644
--- a/my/body/sleep/common.py
+++ b/my/body/sleep/common.py
@@ -7,10 +7,26 @@ class Combine:
         self.modules = modules
 
     @cdf
-    def dataframe(self) -> DataFrameT:
+    def dataframe(self, with_temperature: bool=True) -> DataFrameT:
         import pandas as pd # type: ignore
         # todo include 'source'?
         df = pd.concat([m.dataframe() for m in self.modules])
+
+        if with_temperature:
+            from ... import bluemaestro as BM
+            bdf = BM.dataframe()
+            temp = bdf['temp']
+
+            def calc_avg_temperature(row):
+                start = row['sleep_start']
+                end   = row['sleep_end']
+                if pd.isna(start) or pd.isna(end):
+                    return None
+
+                # on no temp data, returns nan, ok
+                return temp[start: end].mean()
+
+            df['avg_temp'] = df.apply(calc_avg_temperature, axis=1)
         return df
 
     def stats(self) -> Stats: