A: The only way to calibrate a thermometer without ice is to use the hot water method. This method involves setting your thermometer to the temperature of boiling water, 212⁰F or 100⁰C. It is not the safest way to do it but it will work. You need to fill a pot with water and place it on a stove burner and bring the water to a boil, then insert the probe of the thermometer into the boiling water and set the temperature. This way to calibrate a thermometer is not the safest way to do it because you have to place your hands over the boiling water while you calibrate the thermometer. The ice method is the recommended way to calibrate a thermometer.