diff --git a/app/src/main/java/de/apps4ics/mountainnavigation/MainActivity.java b/app/src/main/java/de/apps4ics/mountainnavigation/MainActivity.java
index 0c20a75..45ce31b 100644
--- a/app/src/main/java/de/apps4ics/mountainnavigation/MainActivity.java
+++ b/app/src/main/java/de/apps4ics/mountainnavigation/MainActivity.java
@@ -178,8 +178,8 @@
 
         minWindySpeed = 8; //http://www.wettergefahren-fruehwarnung.de/Artikel/beaufort.html
         if(weatherConfig.unitSystem.equals(WeatherConfig.UNIT_SYSTEM.I)){
-            minHotTemp = 86; //about 30 degree celsius
-            maxColdTemp = 50; //about 10 degree celsius
+            minHotTemp = celsiusToFahrenheit(30);
+            maxColdTemp = celsiusToFahrenheit(10);
         } else {
             minHotTemp = 30;
             maxColdTemp = 10;
@@ -276,6 +276,14 @@
         long f_id = dbHandler.addPoi(fountain);
     }
 
+    public static float celsiusToFahrenheit(float c) {
+        return c * 9.0f/5.0f + 32;
+    }
+
+    public static float fahrenheitToCelsius(float f) {
+        return (f - 32.0f) * 5.0f/9.0f;
+    }
+
     private void toggleDrawerItems(TableLayout layout, int position){
         TableRow tr = (TableRow) layout.getChildAt(0); //TODO is tablerow?
         TextView tv = null;