diff --git a/lib/xmet/igra.py b/lib/xmet/igra.py
index b3d845f..eadc453 100644
--- a/lib/xmet/igra.py
+++ b/lib/xmet/igra.py
@@ -78,11 +78,15 @@ class IGRAReader():
         sample.height_qa   = match['zflag']
         sample.temp        = parse_num(match['temp'], 0.1)
         sample.temp_qa     = match['tflag']
-        sample.humidity    = parse_num(match['rh'], 0.1)
-        sample.dewpoint    = parse_num(match['dpdp'], 0.1)
+        sample.dewpoint    = None
         sample.wind_dir    = parse_num(match['wdir'], 1.0)
         sample.wind_speed  = parse_num(match['wspd'], 0.1)
 
+        dpdp = parse_num(match['dpdp'], 0.1)
+
+        if sample.temp is not None and dpdp is not None:
+            sample.dewpoint = sample.temp - dpdp
+
         return sample
 
     def read(self) -> Sounding: