According to AstroSwami the meaning of your Dream is:
If it is a medical thermometer, you may be afraid someone close to you is sick, or you may be concerned about your own health. Perhaps you wish to make someone better, either physically or emotionally. If you dream of an outdoor thermometer, you might be experiencing extreme heat or cold in your environment. Additionally, dreaming of a high thermometer can mean anger or emotions, while a cold reading thermometer might mean you feel left out, cold or exposed.