The leaf wetness sensor enables the weather station to detect the presence of surface moisture and calculate the duration of wetness. When moisture is present the sensor detects a decrease in electrical resistance. The resistance is displayed as a value between 0 (dry) and 15 (wet). It should be noted that 15 is generally the reading that occurs with showers, sprinkles, and precipitation. With dews, readings most often will be less than 15 unless it is extremely heavy dew. The sensing surface is at an angle of 45 ° and is smooth thus actually dries faster than leaf surfaces. Thus on a sunny morning the sensor may record a dry surface when in fact the grass is still wet with dew. Snow or frost will give a 0 reading if there is no melting or if the snow or frost has already melted off the sensor. The temperature may be below freezing but in the sun the temperature may well be above freezing and the melting snow will be indicated by the sensor.