diff --git a/lib/xmet/skew_t.py b/lib/xmet/skew_t.py
index 1731520..6c92ffd 100644
--- a/lib/xmet/skew_t.py
+++ b/lib/xmet/skew_t.py
@@ -141,7 +141,12 @@ class SkewTGraph():
             sy_last     = sy
             height_last = height
 
-            pressure -= 10.0
+            if pressure == PRESSURE_MIN:
+                break
+            elif pressure - 10.0 < PRESSURE_MIN:
+                pressure = PRESSURE_MIN
+            else:
+                pressure -= 10.0
 
     def draw_adiabats(self,
                       cr: cairo.Context,