The Alfred Horticulture thermo-hygrometer accurately measures humidity and temperature in degrees Celsius or Fahrenheit and has a very easy to understand indicator that indicates if the levels of both measures are adequate or if on the contrary the environment is too dry or humid.Humidity and temperature are measured directly with the sensor integrated into the device. You can measure the temperature and humidity at the same time. Also measure the outside temperature with the probe. This Thermometer / Hygrometer has a memory function of the data. It remembers the maximum and minimum registered for the last time of temperature and humidity.Remember that the maximum temperature with the light on should not go above 25ºC or drop below 16ºC when the light is off. Growing moisture should be between 60-70% and 40-60% in flowering. Requires 2 AG10 batteries, not included.