diff --git a/lib/xmet/skew_t.py b/lib/xmet/skew_t.py
index 5e05c9e..d41f41a 100644
--- a/lib/xmet/skew_t.py
+++ b/lib/xmet/skew_t.py
@@ -4,8 +4,7 @@ import cairo
 from typing import Callable
 
 from xmet.sounding import Sounding
-from xmet.thermo   import pressure_height, lapse, \
-                          LAPSE_RATE_MOIST, LAPSE_RATE_DRY
+from xmet.thermo   import pressure_height, lapse
 
 PRESSURE_MAX  = 1050 # millibar
 PRESSURE_MIN  =  100
@@ -22,9 +21,6 @@ TEMP_CENTER     =   0 # degrees C
 TEMP_STEP       =   5
 TEMP_STEP_COUNT = math.ceil(TEMP_RANGE / TEMP_STEP)
 
-LAPSE_RATE_DRY   = 9.8 / 1000 # degrees C per 1000m
-LAPSE_RATE_MOIST = 4.0 / 1000
-
 def clamp(value, lowest, highest):
     if value < lowest:
         return lowest
@@ -108,8 +104,7 @@ class SkewTGraph():
                      x: float,
                      y: float,
                      start_temp: float,
-                     start_pressure: float,
-                     lapse_rate: float):
+                     start_pressure: float):
         start_height = pressure_height(start_pressure)
         sx_last = None
         sy_last = None
@@ -118,7 +113,7 @@ class SkewTGraph():
 
         while pressure >= PRESSURE_MIN:
             height   = pressure_height(pressure)
-            temp_cur = lapse(start_temp, lapse_rate, height - start_height)
+            temp_cur = lapse(start_temp, height - start_height)
 
             sx, sy = self.sample_to_screen(temp_cur, pressure)
 
@@ -140,7 +135,7 @@ class SkewTGraph():
         cr.set_source_rgba(1.0, 0.2, 0, 0.2)
 
         for temp in range(-140, 140, 10):
-            self.draw_adiabat(cr, x, y, temp, PRESSURE_MAX, LAPSE_RATE_DRY)
+            self.draw_adiabat(cr, x, y, temp, PRESSURE_MAX)
 
         cr.restore()
 
diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 23acabb..f8c2c62 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -1,5 +1,5 @@
-LAPSE_RATE_MOIST = 4.0 # degrees C per km
-LAPSE_RATE_DRY   = 9.8
+LAPSE_RATE_DRY   = 9.8 / 1000 # degrees C per km
+LAPSE_RATE_MOIST = 4.0 / 1000
 
 def vapor_pressure(dewpoint: float) -> float:
     """
@@ -50,9 +50,9 @@ def pressure_height(pressure: float) -> float:
     """
     return (1 - (pressure / 1013.25) ** 0.190284) * 145366.45 * 0.3048
 
-def lapse(temp: float, rate: float, delta: float) -> float:
+def lapse(temp: float, delta: float) -> float:
     """
-    Return the temperature of a parcel cooled at either the dry or moist lapse
-    rate for a given increase in height (in meters).
+    Return the temperature of a parcel cooled at the dry lapse rate for a
+    given increase in height (in meters).
     """
-    return temp - (rate * delta)
+    return temp - (LAPSE_RATE_DRY * delta)