Unfortunately, most grill and smoker thermometers aren't that accurate. In fact, they only measure the heat of the lid's inside instead of the actual cooking space. As a result, the temperature is always off by a few degrees. Additionally, the cooking space can also influence how the thermometer interprets the temperature. If the smoker box is large and the thermometer is placed on the colder side of the griller, the thermometer will display an inaccurate reading. These thermometers also do a poor job of maintaining the temperature inside the smoker grill combo.