A Minimum - Maximum Thermometer is essential to properly monitor the outdoor wintering of bonsai trees.  It shows the current temperature as well as the highest and lowest temperature since it was last reset, which is done by pressing the red button in the center.  The dual scale is from -40 to +120 degrees Fahrenheit, and from -40 to + 50 degrees Centigrade.   This high quality, accurate thermometer is made by West Meters Ltd. of England, and includes a mounting bracket.