diff --git a/things.ino b/things.ino
index d7ce9e1..2bdac9f 100644
--- a/things.ino
+++ b/things.ino
@@ -55,6 +55,7 @@ Ticker ticker;                    // LED status
 WiFiClient wifiClient;
 PubSubClient mqtt_client(wifiClient);
 
+bool dhtvalid = false;                       // indicate if measurement is valid
 float humidity, temperature;                 // raw values from the sensor
 float heatindex;                             // computed value from the sensor
 char str_humidity[10], str_temperature[10];  // rounded values as strings
@@ -108,8 +109,14 @@ void read_sensor() {
 
     // check if any reads failed and exit early (to try again)
     if (isnan(humidity) || isnan(temperature)) {
+      dhtvalid = false;
       Serial.println("Failed to read from DHT sensor!");
+      strcpy(str_humidity, "invalid");
+      strcpy(str_temperature, "invalid");
+      strcpy(str_heatindex, "invalid");
       return;
+    } else {
+      dhtvalid = true;
     }
 
     // convert the floats to strings and round to 2 decimal places