diff --git a/DHT.cpp b/DHT.cpp
index 92ebcf8..f349934 100644
--- a/DHT.cpp
+++ b/DHT.cpp
@@ -21,7 +21,7 @@ void DHT::begin(void) {
   _lastreadtime = 0;
 }
 
-//boolean S == Scale.  True == Farenheit; False == Celcius
+//boolean S == Scale.  True == Fahrenheit; False == Celcius
 float DHT::readTemperature(bool S) {
   float f = NAN;
 
@@ -78,18 +78,34 @@ float DHT::readHumidity(void) {
   return f;
 }
 
-float DHT::computeHeatIndex(float tempFahrenheit, float percentHumidity) {
+//boolean isFahrenheit: True == Fahrenheit; False == Celcius
+float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
   // Adapted from equation at: https://github.com/adafruit/DHT-sensor-library/issues/9 and
   // Wikipedia: http://en.wikipedia.org/wiki/Heat_index
-  return -42.379 +
-           2.04901523 * tempFahrenheit +
-          10.14333127 * percentHumidity +
-          -0.22475541 * tempFahrenheit*percentHumidity +
-          -0.00683783 * pow(tempFahrenheit, 2) +
-          -0.05481717 * pow(percentHumidity, 2) +
-           0.00122874 * pow(tempFahrenheit, 2) * percentHumidity +
-           0.00085282 * tempFahrenheit*pow(percentHumidity, 2) +
-          -0.00000199 * pow(tempFahrenheit, 2) * pow(percentHumidity, 2);
+  if (!isFahrenheit) {
+    // Celsius heat index calculation.
+    return -8.784695 +
+             1.61139411 * temperature +
+             2.338549   * percentHumidity +
+            -0.14611605 * temperature*percentHumidity +
+            -0.01230809 * pow(temperature, 2) +
+            -0.01642482 * pow(percentHumidity, 2) +
+             0.00221173 * pow(temperature, 2) * percentHumidity +
+             0.00072546 * temperature*pow(percentHumidity, 2) +
+            -0.00000358 * pow(temperature, 2) * pow(percentHumidity, 2);
+  }
+  else {
+    // Fahrenheit heat index calculation.
+    return -42.379 +
+             2.04901523 * temperature +
+            10.14333127 * percentHumidity +
+            -0.22475541 * temperature*percentHumidity +
+            -0.00683783 * pow(temperature, 2) +
+            -0.05481717 * pow(percentHumidity, 2) +
+             0.00122874 * pow(temperature, 2) * percentHumidity +
+             0.00085282 * temperature*pow(percentHumidity, 2) +
+            -0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);
+  }
 }
 
 boolean DHT::read(void) {
diff --git a/DHT.h b/DHT.h
index 9cf381d..41e66fe 100644
--- a/DHT.h
+++ b/DHT.h
@@ -42,7 +42,7 @@ class DHT {
    float readTemperature(bool S=false);
    float convertCtoF(float);
    float convertFtoC(float);
-   float computeHeatIndex(float tempFahrenheit, float percentHumidity);
+   float computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit=true);
    float readHumidity(void);
    boolean read(void);
 
diff --git a/examples/DHTtester/DHTtester.ino b/examples/DHTtester/DHTtester.ino
index ba70cf5..f397f0a 100644
--- a/examples/DHTtester/DHTtester.ino
+++ b/examples/DHTtester/DHTtester.ino
@@ -37,9 +37,9 @@ void loop() {
   // Reading temperature or humidity takes about 250 milliseconds!
   // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
   float h = dht.readHumidity();
-  // Read temperature as Celsius
+  // Read temperature as Celsius (the default)
   float t = dht.readTemperature();
-  // Read temperature as Fahrenheit
+  // Read temperature as Fahrenheit (isFahrenheit = true)
   float f = dht.readTemperature(true);
 
   // Check if any reads failed and exit early (to try again).
@@ -48,9 +48,10 @@ void loop() {
     return;
   }
 
-  // Compute heat index
-  // Must send in temp in Fahrenheit!
-  float hi = dht.computeHeatIndex(f, h);
+  // Compute heat index in Fahrenheit (the default)
+  float hif = dht.computeHeatIndex(f, h);
+  // Compute heat index in Celsius (isFahreheit = false)
+  float hic = dht.computeHeatIndex(t, h, false);
 
   Serial.print("Humidity: ");
   Serial.print(h);
@@ -61,6 +62,8 @@ void loop() {
   Serial.print(f);
   Serial.print(" *F\t");
   Serial.print("Heat index: ");
-  Serial.print(hi);
+  Serial.print(hic);
+  Serial.print(" *C ");
+  Serial.print(hif);
   Serial.println(" *F");
 }