Interrupt triggering using DHT-11
You can't use an interrupt the way you are attempting to. Attaching an interrupt to a pin like that will cause the interrupt to trigger any time the digital pin's value changes. The DHT11 uses serial communication to send temp values to the Arduino. Serial communication uses lots and lots of on/off pulses on the signal line to send characters of data. Your interrupt will fire every time the DHT11 toggles the signal line.

You need to read the temp from the DHT11 in your loop, and then add an if statement that does what you want when the temp exceeds your threshold. (It looks like you just need to get rid of the attachInterrupt() call, and instead call IntCallback() every couple of seconds.