diff --git a/README.md b/README.md
index 10d8683..159e744 100644
--- a/README.md
+++ b/README.md
@@ -202,6 +202,7 @@ To specify your own custom output format, use the special `%`-notation:
     m    Moonphase 🌑🌒🌓🌔🌕🌖🌗🌘,
     M    Moonday,
     p    precipitation (mm),
+    o    Probability of Precipitation,
     P    pressure (hPa),
 ```
 
diff --git a/lib/wttr_line.py b/lib/wttr_line.py
index 5ede450..48fb6a1 100644
--- a/lib/wttr_line.py
+++ b/lib/wttr_line.py
@@ -101,6 +101,16 @@ def render_precipitation(data, query):
         answer += 'mm'
     return answer
 
+def render_precipitation_chance(data, query):
+    """
+    precipitation chance (o)
+    """
+
+    answer = data.get('chanceofrain', '')
+    if answer:
+        answer += '%'
+    return answer
+
 def render_pressure(data, query):
     """
     pressure (P)
@@ -189,6 +199,7 @@ FORMAT_SYMBOL = {
     'M':    render_moonday,
     's':    render_sunset,
     'p':    render_precipitation,
+    'o':    render_precipitation_chance,
     'P':    render_pressure,
     }